KR100968387B1 - Methods and apparatus for supporting uplinks with remote base stations - Google Patents

Abstract

A wireless terminal using OFDM signaling supporting both terrestrial and satellite base station connectivity operates using conventional access probe signaling in a first mode of operation to establish a timing synchronized wireless link with a terrestrial base station. In a second mode of operation, used to establish a timing synchronized wireless link with a satellite base station, a slightly modified access protocol is employed. The round trip signaling time and timing ambiguity between a wireless terminal and a satellite base station is substantially greater than with a terrestrial base station. The modified access protocol uses coding of access probe signals to uniquely identify a superslot index within a beaconslot. The modified protocol uses multiple access probes with different timing offsets to further resolve timing ambiguity and allows the satellite base station access monitoring interval to remain small in duration. Terrestrial base station location/connection information is used to estimate initial timing.

Description

METHODS AND APPARATUS FOR SUPPORTING UPLINKS WITH REMOTE BASE STATIONS}

Field of invention

The present invention is directed to a method and apparatus that can be used to implement an OFDM system that uses OFDM tones to convey uplink signals to terrestrial base stations and / or satellite base stations.

background

Regardless of the location of the handheld communication device in the wide area, the ability to communicate using that communication device, for example a portable telephone, is of great value. The value of such a device is important for military applications as well as for conventional consumer based applications.

Terrestrial base stations are installed at various indicator-based locations to support voice and / or data services. In general, such base stations have a coverage area of at most several miles. Thus, the distance between a conventional cell phone and a base station during use is typically only a few miles. Assuming a relatively small distance between cell phones and terrestrial base stations during normal use, handheld cell phones generally use a bandwidth that is relatively wide and in many cases can support a relatively high data rate, e.g. Has enough power to transmit to the base station via.

In one known system based on the use of terrestrial base stations, a plurality of OFDM tones, for example in some cases seven or more tones, are used in parallel by the wireless terminal to transmit user data to the base stations. In known systems, in general, user data to be transmitted on the uplink and control signals to be transmitted on the uplink are individually coded. In a known system, a wireless terminal may be assigned a dedicated tone for uplink control signaling to uplink traffic segments corresponding to tones to be allocated in response to one or more uplink requests sent to a terrestrial base station. In a known system, uplink traffic channel segment assignment information is broadcast to wireless terminals that monitor assignment signals that may indicate assignment of uplink traffic channel segments in response to a transmitted request. Periodically, the base station of a known system also receives signals that may be used for timing synchronization by timing synchronization signals, referred to as beacon signals, that circulate over a period of time, often referred to as a beacon slot, Broadcast.

Terrestrial base stations are useful in areas where the population is sufficient to justify the cost of terrestrial base stations, but in many locations on the planet, it is practical to deploy permanent terrestrial base stations due to insufficient commercial justification and / or geographic issues in deploying the base stations. Is not In physically uninhabitable areas, such as, for example, oceans, desert areas, and / or areas covered by ice sheets, deploying and maintaining terrestrial base stations may not be difficult or practical.

The lack of base stations in some geographic areas leads to "dead zones" that are impossible to communicate using cell phones. To attempt to eliminate the number of areas where cell phone coverage is missing, companies may continue to deploy new base stations, but for the reasons mentioned above, in the near future, cell phone from terrestrial base stations Many areas of the planet may be left where coverage cannot be obtained.

An alternative to terrestrial base stations is to use satellites as base stations. Given the cost of launching satellites, satellite base stations are very expensive to deploy. In addition, the space on the planet on which stationary satellites can be placed is limited. Although the satellite in geostationary orbit has the advantage that it is in a fixed position with respect to the earth, lower earth orbit satellites may also be deployed, but such satellites are expensive to deploy and are lower in their initial orbit than satellites. Will remain in orbit for a shorter period of time. The distance from the earth's surface to which the mobile phone may be located is about 22,226 miles, for example, but some estimates suggest that 22,300 miles is a better estimate. Taking this into account, the diameter of the earth is about 7,926 miles. Unfortunately, in the case of satellite base stations, the distance the signal has to travel is considerably longer than the distance the signal typically travels to reach a conventional terrestrial base station, which is typically at most several miles.

As can be seen, assuming a distance to the geostationary orbit, it is often necessary to transmit a signal to the satellite at a higher power level than required to transmit the signal to the terrestrial base station. As a result, most satellite phones are relatively large and bulky compared to conventional phones due to the size of the batteries, power amplifiers, and other circuits used to implement the cell phones. The need for relatively large and therefore often bulky power amplifiers arise in part from the fact that many conventional communication systems have less than an ideal peak to average power ratio. Relatively large peak-to-average power ratios require larger amplifiers to be included to support the peak power output than can be used in the case of the same average power output, but here the peak-to-average power ratio is lower.

Assuming a large distance to the satellite base station and / or a relatively large cell size compared to the terrestrial base station, the uplink timing synchronization used for the terrestrial base station using the OFDM signal in the uplink is sufficient for communication with the satellite base station. It may not be enough to achieve link symbol timing synchronization. Thus, there is a need for an improved method of supporting OFDM uplink signaling, including an improved timing synchronization method and / or apparatus that can be used with a long round trip delay.

SUMMARY OF THE INVENTION

The present invention relates to a communication method and apparatus suitable for use in a communication system comprising base stations and / or remote base stations with large coverage areas.

The method and apparatus of the present invention can be used to synchronize uplink transmission timing of a communication device, eg, a wireless terminal, with base station timing. The beacon signal transmitted from the base station in the downlink may be used to facilitate the timing synchronization process. A wide variety of beacon signals can be used to support the methods and apparatus of the present invention. In some OFDM embodiments, beacon signals are transmitted in the downlink using one or several tones for one or several consecutive time periods. In some embodiments, the beacon signals are implemented as a single tone signal transmitted during one, two, or three consecutive OFDM symbol transmission times, depending on the particular embodiment.

As will be described below, in an OFDM system, the transmission of signals by a communication device to a base station is performed at a synchronization level within the cyclic prefix duration for OFDM symbols transmitted in a synchronized manner, for example, a cyclic prefix. Must reach the base station from which they are transmitted.

The methods and apparatus of the present invention support and permit such levels of synchronization to be achieved even with very remote base stations through various methods and techniques that can be used alone or in combination to achieve the desired level of synchronization. While most of the description herein focuses on downlink timing structure and beacon slots occurring in the downlink, it can be seen that the base station uplink timing has a fixed known relationship with respect to the downlink timing. The received signal and the time at which the signal is received at the base station can be measured in terms of downlink symbol transmission timing and downlink transmission slot where the signal is received on the uplink.

The uplink timing structure of the present invention allows for an access interval that will occur at periodic intervals in which communication devices that are not synchronized with the base station may generate an access request in terms of uplink transmission timing. Such a request may be competition based. The base station of the present invention is monitored during the access interval for the access request and responds with timing corrections and / or other information. The access interval is the interval while the elements of the uplink timing structure occur in a fixed known relationship to the downlink timing. In general, each access interval has a duration that is less than the duration of the downlink superslot in duration.

In various embodiments, each of the superslots includes multiple OFDM symbol transmission time periods, eg, a fixed number of OFDM symbol transmission time periods. In some but not all implementations, each uplink superslot includes an access interval. The access interval in the uplink occurs at a fixed known position with respect to the start of the beacon signal occurring in the downlink superslot and downlink. Thus, the downlink timing structure can be used as a reference for controlling uplink transmission timing as described below.

Many of the features of the present invention relate to timing synchronization. Other aspects of the present invention relate to a particular access method and apparatus that can be used to register and achieve timing synchronization with a remote base station, eg, a base station 100 miles or more from the location of a wireless terminal.

In various embodiments, the remote base station is a base station with a minimum distance from the wireless terminal during use, measured in terms of tens, hundreds, or even thousands of miles. The stationary satellite base station is an example of a remote base station. Stationary satellite base stations are located thousands of miles above the earth's surface, in which case the minimum distance to the communication device on the earth's surface or even on a commercial aircraft is measured in thousands of miles. This is in contrast to a near base station, which may be, for example, a terrestrial base station located within a maximum of 50 miles but more typically within a maximum of 5 miles of a wireless terminal during normal use.

The method and apparatus of the present invention, including the cell phone of the present invention, are well suited for use in a communication system having both terrestrial and satellite base stations, while the method and apparatus of the present invention provide output power for a fixed amount of bandwidth. It is well suited for a wide range of communication applications where a large difference in the amount of is required. In the satellite example, a much larger amount of output power for a fixed amount of bandwidth is more successful for the satellite base station than is required for successful uplink signaling using the same amount of transmission bandwidth for the terrestrial base station. Required for uplink signaling.

Various aspects of the present invention relate to methods and apparatus that can be used to implement portable communication devices capable of communicating with remote base stations and relatively close base stations, such as satellite base stations and terrestrial base stations. A system implemented in accordance with the present invention may include a plurality of nearby base stations and remote base stations. In one such system, a terrestrial base station is used to provide sufficient communication traffic to communication coverage to justify the deployment of the terrestrial base station. Satellite base stations are used to fill coverage in areas where terrestrial base stations are not deployed due to, for example, the nature of the physical environment, the lack of sites for the base stations, or other causes. The portable communication device in the example system can communicate with both the terrestrial base station and the satellite base station, for example, by switching between different modes of operation.

As will be discussed below, in various embodiments, the system is implemented as an OFDM system. In some embodiments, OFDM signaling is used for uplink signaling as well as downlink signaling. First and second modes of OFDM uplink operation are supported.

During normal operation with a terrestrial base station, a wireless terminal uses multiple tones in parallel in the uplink to transmit user data on multiple tones simultaneously to the base station. This allows relatively high data rates to be supported. When operating in the multi-tone mode, the average peak to average power ratio is the first ratio during a portion of the time user data is transmitted over multiple tones. As will be described below, for example, when operating in a single tone mode of operation used to communicate with a satellite base station, a second, lower peak to average power ratio is achieved. Thus, when operating in single tone mode, the power amplifier can be used in a more efficient manner. In various embodiments, the difference in peak-to-average power ratio between the operation of the multi-tone mode and the operation of the single-tone mode achieved over several symbol time periods is at least 4 dB and is generally 6 dB.

Single-tone-mode is a method of operating the wireless terminal to maximize the uplink power budget coverage of the OFDM wireless terminal under the conventional power limitations encountered when communicating with terrestrial base stations. This mode is suitable for low rate data of multi-tone channels, ie, voice link, where ACK is not supported.

In single tone mode, the terminal will transmit an OFDM single tone at a time. This tone is represented as a single constant logical tone, but in various embodiments, the tone can hop from physical tone to physical tone on a dwell boundary when matched with other OFDM channels used in some systems. . In one embodiment, this logical tone replaces the UL-DCCH channel used to communicate with the terrestrial base station, thus maintaining compatibility with other OFDM users operating in the standard multi-tone mode.

In some embodiments, the content of the single tone uplink channel used by the wireless terminal comprises a multiplex of control data and user data. Such a multiplex may exist at the field level in the code word, ie some bits from the channel coding block are used to represent the control data and others represent user data. However, in another embodiment, multiplexing in a single tone uplink channel is present at the code word level, for example, control data is coded in the channel coding block, user data is coded in the channel coding block, The blocks are multiplexed together for transmission on a single tone uplink channel. In one embodiment, if a single tone channel is not fully occupied with user data (eg, during silence suppression of a voice call), it is possible to blank the transmitter during unnecessary transmission symbols, This conserves transmitter power since no signal needs to be transmitted during this period. User data may be multiplexed packet data or regularly scheduled voice data, or a mixture thereof.

For terminals operating in single-tone mode, downlink acknowledgment signals cannot be transmitted on separate channels as is done in multi-tone mode, so the downlink acknowledgment is sent to a logical single tone uplink channel tone. Multiplexed or ACK is not used. In such a case, the base station may assume that the downlink traffic channel segments have been successfully received by the wireless terminal explicitly requesting retransmission, if necessary.

According to the present invention, a wireless terminal operating in single tone mode may achieve an advantage in the power transmitted while using standard OFDM components to implement a transmitter. In standard mode, the averaged power typically transmitted is the peak-to-average ratio (PAR), i.e., the power amp of the transmitter to avoid peak clipping, which typically allows for 9 dB and may cause excessive out-of-band emissions. Limited below peak power capability. In the single tone mode, in various embodiments, the PAR is limited to about 3 dB, so the average transmit power can be increased by nearly 6 dB without increasing the probability of clipping.

In the frequency hop (change in physical tone corresponding to a single logical tone occurs at the dwell boundary), the phase of the transmitted waveform can be controlled to be phase continuous over frequency. This gives the carrier frequency of the tone during the cyclic expansion of the OFDM symbol from one symbol transmitted in the uplink to the next symbol so that the signal phase at the end of the symbol is at the same desired value as the start phase of the subsequent symbol. It may be achieved by a change and is achieved in some embodiments rather than all required embodiments. This phase continuous operation will cause the PAR of the signal to be constrained to 3 dB.

OFDM over geostationary satellites is made possible by several variations of the existing basic OFDM communication protocol. Due to the very long round-trip time (RTT), there is little or no value of the slave acknowledgment for the traffic channel. Thus, in some embodiments of the invention, downlink acknowledgments are not transmitted when operating in single tone uplink mode. In some such embodiments, the downlink acknowledgment is replaced with a repeat request mechanism in which the request is sent in the UL for repeated transmission of data that was not successfully received.

Many features, advantages, and embodiments of the invention are described in the following detailed description.

Brief description of the drawings

1 is a diagram of an exemplary communication system implemented in accordance with the present invention and using the method of the present invention.

2 is a diagram of an exemplary base station, eg, a ground based base station, implemented in accordance with the present invention and using the method of the present invention.

2A is a diagram of an exemplary base station, eg, satellite based base station, implemented in accordance with the present invention and using the method of the present invention.

3 is a diagram of an exemplary wireless terminal, eg, a mobile node, implemented in accordance with the present invention and using the method of the present invention.

4 is a diagram illustrating exemplary uplink information bit encoding for an exemplary WT, eg, an MN, operating in a single-tone uplink mode of operation, in accordance with various embodiments of the present invention.

5 is an illustration of an exemplary OFDM wireless multiple access communication system including a hybrid of base stations that are both ground-based and satellite-based, in accordance with various embodiments of the present invention.

FIG. 6 is a diagram illustrating an exemplary backhaul interconnect diagram between the various satellite based base stations and ground based base stations of FIG. 5.

7 is a flowchart of an exemplary method of operating a wireless terminal, eg, a mobile node, in accordance with the present invention.

7A is a significantly different between the exemplary satellite base station and the different mobile nodes located at different points in the cellular coverage area of the satellite base station on the surface of the earth, resulting in timing synchronization considerations solved in accordance with the method and apparatus of the present invention. A diagram illustrating signal path lengths and relatively long round trip signaling time.

FIG. 8 illustrates an exemplary hybrid system including both terrestrial base stations and satellite based base stations, and wireless terminals that use terrestrial base station location information to reduce round trip timing ambiguity with respect to satellite base stations.

8A illustrates an embodiment in which multiple terrestrial base stations are associated with the same satellite base station coverage area, wherein terrestrial base station information and / or access information is used to reduce WT / satellite base station timing ambiguity.

9 illustrates that in an exemplary satellite / terrestrial hybrid wireless communication system, the round trip signal delay between the satellite base station and the ground-based wireless terminal is greater than the typical superslot time interval used in some land-based wireless communication systems. It is a figure showing.

10 illustrates coding an access probe signal with information identifying a larger relative time interval in a timing structure, eg, a relative time interval value, eg, a superslot index value, in a beacon slot, in accordance with the present invention. Characteristic diagrams wherein the coded information is used in an access process to determine timing synchronization between a satellite base station and a WT.

FIG. 11 illustrates the characteristic of using multiple access probe signals with different timing offsets such that timing synchronization between satellite base station and WT can be further resolved within a smaller time interval, in accordance with the present invention. to be.

12 further illustrates the concept of a wireless terminal transmitting multiple access probes with different timing offsets to a satellite base station, in accordance with the present invention.

13 is a diagram illustrating exemplary access signaling in accordance with the method of the present invention.

14 is a diagram illustrating exemplary access signaling in accordance with the method of the present invention.

15 is a diagram illustrating exemplary access signaling in accordance with the method of the present invention.

16, including the combination of FIGS. 16A and 16B, is a flowchart of an exemplary method of operating a wireless terminal to access a base station and perform a timing synchronization operation in accordance with the present invention.

17, including the combination of FIGS. 17A and 17B, is a flowchart of an example method of operating a communications device for use in a communications system.

18 is a flowchart of an example method of operating an example communication device in accordance with the present invention.

19 is a flowchart of an example method of operating an example communication device in accordance with the present invention.

20 is a flowchart of an exemplary method of operating a wireless communication terminal in a system in accordance with the present invention.

21 is a diagram of an exemplary wireless terminal, eg, a mobile node, implemented in accordance with the present invention.

22 is a flowchart of an exemplary method of operating a base station in accordance with the present invention.

23 is a diagram of an exemplary wireless terminal, eg, a mobile node, implemented in accordance with the present invention.

24 is a diagram of an exemplary terminal, eg, a mobile node, implemented in accordance with the present invention.

25 is a diagram of an exemplary base station implemented in accordance with the present invention and using the method of the present invention.

details

1 is a diagram of an exemplary wireless communication system 100 implemented in accordance with the present invention and using the method of the present invention. Example system 100 is an example orthogonal frequency division multiplexing (OFDM) multiple access spread spectrum wireless communication system. Example system 100 includes a plurality of base stations 102, 104 and a plurality of wireless terminals 106, 108, eg, mobile nodes. Various base stations 102, 104 may be coupled together via a backhaul network. Mobile nodes (MN1 106, MN N 108) move throughout the system and may use a base station as the network connection point of that mobile node in the coverage area of the base station where the mobile node is currently located. Some of the base stations are terrestrial based base stations, eg BS 102, and some of the base stations are satellite based base stations, eg BS 104. From the perspective of the MNs 106, 108, the terrestrial base station is considered as the near base station 102, while the satellite based base station is considered as the remote base station 104. The MNs 106 and 108 are in two different modes of operation, e.g., an uplink multi-tone mode of operation tailored to power and timing considerations in communication with a near base station, e. And the ability to operate in an uplink single tone mode of operation tailored to power and timing considerations in communication with a remote base station, eg, satellite base station 104. At some time, MN1 106 may be coupled to satellite BS 104 via wireless link 114, and may be operating in an uplink single tone mode of operation. At other times, MN1 106 may be coupled to terrestrial base station 102 via wireless link 110 and may be operating in a more conventional multi-tone uplink mode of operation. Similarly, at some time, MN N 108 may be coupled to satellite BS 104 via wireless link 116 and may be operating in an uplink single tone mode of operation. At other times, MN N 108 may be coupled to terrestrial base station 102 via wireless link 112 and may be operating in a more conventional multi-tone uplink mode of operation.

Other MNs may exist in a system that supports communication with one type of base station, eg, terrestrial base station 102, but does not support communication with another type of base station, eg, satellite base station 104.

2 is a diagram of an exemplary base station 200, for example a land based base station, implemented in accordance with the present invention and using the method of the present invention. Example base station 200 may be a proximity base station, eg, terrestrial base station 102, of example system 100 of FIG. 1. Since base station 200 provides network access to the WT, base station 200 is often referred to as an access node. Base station 200 couples together via receiver 202, transmitter 204, processor 206, I / O interface 208, and bus 212 through which various elements may exchange data and information. Memory 210. Receiver 202 includes a decoder 214 for decoding received uplink signals from WTs. Transmitter 204 includes an encoder 216 that encodes downlink signals to be transmitted with WTs. Each of receiver 202 and transmitter 204 is coupled to antennas 218, 220, where uplink signals are received in WTs and downlink signals are transmitted in WT, respectively. In some embodiments, the same antenna is used for receiver 202 and transmitter 204. I / O interface 208 couples base station 200 to the Internet / other network nodes. Memory 210 includes routine 222 and data / information 224. The processor 206, eg, the CPU, executes the routine 222 in the memory 210 and uses the data / information 224 to control the operation of the base station 200 and implement the method of the present invention. The routine 222 includes a communication routine 226 and a base station control routine 228. The communication routine 226 implements various communication protocols used by the base station 200. Base station control routine 228 includes scheduler module 230, downlink control module 232, and uplink multi-tone user control that assign the uplink segment and the downlink segment to the WT, including the uplink traffic channel segment. Module 234. The downlink control module 232 is configured to download the downlink to the WT, including beacon signaling, pilot signaling, allocation signaling, downlink traffic channel segment signaling, and an automatic retransmission mechanism for the downlink traffic channel segment according to the received ack / nak. Control link signaling. The uplink multi-tone user control module 234 is configured for uplinks assigned by operations on WTs operating in a multi-tone uplink mode, eg, access operations, assignments that vary between different WTs over time. Dedicated control channel using uplink traffic channel user data from a WT delivered simultaneously on multiple tones, for example seven tones, in a traffic channel segment, timing synchronization operation, and dedicated logical tones Control the processing of control information from the WT delivered via.

The data / information 224 may include a plurality of sets of information (user 1 / MN session A session B data / information 238, user N / corresponding to wireless terminals using the base station 200 as their network connection point). User data / information 236, including MN session X data / information 240. Such WT user data / information may include, for example, WT identifiers, routing information, segment allocation information, user data / information such as data packets such as voice information, text, video, music, and coded blocks of information. It may also include. Data / information 224 also includes system information 242, including multi-tone UL user frequency / timing / power / tone hopping / coding structure information 244.

2A is a diagram of an exemplary base station 300, eg, satellite based base station, implemented in accordance with the present invention and using the method of the present invention. The example base station 300 may be the BS 104 of the example system 100 of FIG. 1. Base station 300 is often referred to as an access node because that base station provides network access to the WT. Base station 300 includes a receiver 302, a transmitter 304, a processor 306, and a memory 308 that is coupled together via a bus 310 through which various elements may exchange data and information. . Receiver 302 includes a decoder 312 that decodes received uplink signals from WTs. Transmitter 304 includes an encoder 314 that encodes downlink signals to be transmitted with WTs. Each of receiver 302 and transmitter 304 is coupled to antennas 316, 318, where uplink signals are received from WTs and downlink signals are transmitted to WTs, respectively. In some embodiments, the same antenna is used for receiver 302 and transmitter 304. In addition to communicating with the WTs, the base station 300 may communicate with other network nodes, eg, a ground station having a directional antenna and a high capacity link, which may be connected to other network nodes, eg For example, it is coupled to other base stations, routers, AAA servers, home agent nodes and the Internet. In some embodiments, the same receiver 302, transmitter 304, and / or antenna described above with respect to the BS-WT communication link are used for the BS-network node ground station link, but in other embodiments, separate elements are Used for different functions. Memory 308 includes routine 320 and data / information 322. The processor 306, eg, the CPU, executes the routine 320 in the memory 308 and uses the data / information 322 to control the operation of the base station 300 and implement the method of the present invention. Memory 308 includes a communication routine 324 and a base station control routine 326. The communication routine 324 implements various communication protocols used by the base station 300. The base station control routine 326 may include a scheduler module 328, a downlink control module 330, a single module that assigns the downlink segment to the WT and reschedules the downlink segment for the WT in response to a received request for retransmission. Uplink tone user control module 332, and network module 344. The downlink control module 330 controls downlink signaling for the WT, including beacon signaling, pilot signaling, downlink segment allocation signaling, and downlink traffic channel segment signaling. The single UL tone user control module 332 includes operations including allocating a single dedicated logical tone to the WT user for use in uplink signaling, including both user data and control information, and the network connection point of the WT. Perform a timing synchronization operation with the WT seeking to use the BS as a BS. The network module 334 controls the operation regarding the I / O interface with the network node ground station link.

The data / information 322 includes a plurality of sets of information (user 1 / MN session A session B data / information 338, corresponding to those wireless terminals using the base station 300 as a network connection point of the wireless terminals, User data / information 366, including user N / MN session X data / information 340. Such WT information may include, for example, data packets such as WT identifiers, routing information, assigned uplink single logical tones, downlink segment allocation information, user data / information such as voice information, text, video, music, etc. And a coded block of information. Data / information 322 also includes system information 342, including single-tone UL user frequency / timing / power / tone hopping / coding structure information 344.

3 is a diagram of an exemplary wireless terminal 400, eg, a mobile node, implemented in accordance with the present invention and using the method of the present invention. The example WT 400 may be any MN of the MNs 106, 108 of the example system 100 of FIG. 1. The example wireless terminal 400 includes a receiver 402, a transmitter 404, a processor 406, and a memory 408 coupled together via a bus 410 through which various elements may exchange data / information. It includes. Receiver 402 coupled to receive antenna 412 includes a decoder 414 that decodes downlink signals received from BSs. Transmitter 404 coupled to transmit antenna 416 includes an encoder 418 that encodes uplink signals to be transmitted to the BSs. In some embodiments, the same antenna is used for receiver 402 and transmitter 404. In some embodiments, omni-directional antennas are used.

In addition, the transmitter 404 includes a power amplifier 405. The same power amplifier 405 is used by the WT 400 for both the multi-tone uplink mode of operation and the single tone uplink mode of operation. For example, in a multi-tone uplink mode of operation in which uplink traffic channel segments may typically use 7, 14, or 28 tones simultaneously, the power amplifier is configured such that 28 signals corresponding to 28 tones are simultaneously structured. It is necessary to accommodate the peak conditions to sort by, which tends to limit the average output level. However, when the WT 400 is operated in a single uplink tone mode of operation using the same power amplifier, the concept of structural alignment between signals from different tones is not an issue, and average power output level for the amplifier. Can be significantly increased over the multi-tone mode of operation. This approach according to the present invention allows a conventional terrestrial mobile node that is used to deliver uplink signals to the satellite base station at substantially increased distance and is configured with minor modifications.

Memory 408 includes routine 420 and data / information 422. The processor 406, eg, the CPU, executes the routine 420 in the memory 408 and uses the data / information 422 to control the operation of the wireless terminal 400 and implement the method of the present invention. do. The routine 420 includes a communication routine 424 and a wireless terminal control routine 426. The communication routine 424 implements various communication protocols used by the wireless terminal 400. The wireless terminal control routine 426 includes an initialization module 427, a handoff module 428, an uplink mode switching control module 430, an uplink single tone mode module 432, an uplink multi-tone mode module ( 434, uplink tone hopping module 436, coding module 438, and modulation module 440.

The initialization module 427 is a wireless terminal that seeks to establish an wireless communication link with a base station and an operation relating to the start of a wireless terminal, including, for example, starting from power off to power on with respect to an operating state ( 400 to control the operation. The handoff module 428 controls the operation regarding handoff from one base station to another, for example, the WT 400 may be presently connected with the terrestrial base station, but for handoff to the satellite base station. May be related. The uplink switching control module 430 is configured to switch between different modes of operation, e.g., from a multi-tone uplink mode of operation, when the wireless terminal switches from communicating with the ground base station to communicating with the satellite base station. Controls the switching of the operation to single tone uplink mode. Uplink single tone mode module 432 includes modules used in single tone mode of operation with respect to satellite base stations, while UL multi-tone mode module 434 is used in multi-tone mode of operation with respect to terrestrial base stations. Contains modules

Uplink single tone mode module 432 includes user data transmission control module 442, transmission power control module 444, control signaling module 446, UL single tone determination module 448, control data / user data multiplexing. Module 450, DL traffic channel retransmission request module 452, dwell boundary and / or inter-symbol boundary carrier coordination module 454, and access module 456. The user data transmission module 442 controls the operation on the uplink user data while in the single tone mode of operation. The transmit power control module 444 controls the transmission of power during the single tone uplink mode to produce an average peak to average power ratio that is at least 4 dB lower than the peak to average power ratio maintained during the multi-tone uplink mode of operation. Keep it. The control signaling module 446 controls signaling during the single tone mode of operation, which control operation is an uplink transmitted from the WT 400 when the operation switches from the multi-tone mode of operation to the single tone mode of operation. Reducing the number and / or frequency of the control signals. The uplink single tone determination module 448 determines a single logical tone in the uplink timing structure that is assigned to the WT for use for uplink signaling, for example, via association with a base station assigned WT identifier. Control data / user data multiplexing module 450 multiplexes control data bits and user data information bits that provide a combined input that may be coded as a block. The downlink traffic channel retransmission request module 452 may not successfully decode downlink traffic channel segments if, for example, the WT considers that the data will still be valid during the large delay of the associated source due to the long round trip signaling time. Issues a request for resend Dwell boundary carrier adjustment module 454 slightly changes the carrier frequency of the tone during cyclic expansion of the OFDM symbol ending the dwell such that the signal phase at the end of the symbol is the same desired value as the start phase of the subsequent symbol. . In this manner, in accordance with the nature of some embodiments of the present invention, at the frequency hop, the phase of the transmitted waveform can be controlled to be phase continuous over frequency. In some embodiments, multiple included in each of the consecutive OFDM symbols, for example, to provide continuity between successive uplink OFDM symbols transmitted by the WT on the uplink during a single UL tone mode of operation. As part of the partial cyclic prefix, frequency adjustment is performed. This continuity between symbols of the signal is advantageous in maintaining peak power level control, which affects the level at which the power amplifier 405 can be driven while in single tone mode of operation.

Access module 456 controls the operation associated with establishing a new wireless link with a satellite base station. Such an operation may include, for example, a timing synchronization operation including access probe signaling in accordance with various aspects of some embodiments of the invention. For stationary satellites with a beam covering a large geographic area, there may be a significant difference in the round trip time between the center and the edge of the beam. To resolve this RTT ambiguity, a range scheme that can resolve several milliseconds of delta-RTT is used. For example, the timing structure may be divided into different time segments such as, for example, a superslot, and different coding of the access probe signal may be used for different superslots, where the superslot is 114 consecutive OFDM symbol transmission time interval. This can be used to cause the timing ambiguity between the WT and the satellite BS to resolve within the superslot. In addition, repeated access attempts at various time offsets may be repeatedly attempted to cover superslot ambiguity (eg, <11.4 msec). In some embodiments, the position with respect to the last terrestrial BS detected may be used to form an initial round trip time estimate (WT-SAT BS-WT), which is estimated by access signaling typically used by terrestrial base stations. You can compress the range within the supported range.

The uplink multi-tone module 434 includes a user data transmission control module 458, a transmission power control module 460, a control signaling module 462, an uplink traffic channel request module 464, an uplink traffic channel tone A set determination module 466, an uplink traffic channel modulation / coding selection module 468, a downlink traffic channel ack / nak module 470, and an access module 472. The user data transmission control module 458 includes operations including controlling transmission of uplink traffic channel segments assigned to the WT.

User data transmission control module 458 controls uplink transmission related operations of user data in a multi-tone mode of operation, where user data is delivered in an uplink traffic channel segment temporarily assigned to the WT, and multiple Contains signals to be transmitted simultaneously using the tones. The transmit power control module 460 adjusts the output power level in accordance with, for example, the receiving base station uplink power control signal and in view of not exceeding the power amplifier's peak power output capability, for example. Adjust to control the uplink transmit power level in the multi-tone mode of uplink operation. The control signaling module 462 controls the power and timing control signaling operation while in the multi-tone uplink mode of operation, wherein the rate of control signaling is higher than the rate in the single-tone uplink mode of operation. In some embodiments, control signaling module 462 uses, for example, the use of a dedicated control channel logical tone dedicated to the WT by the BS for use in uplink control signaling, for example corresponding to the BS assigned WT identifier. It includes. Control signaling module 462 may code the control information for transmission in the uplink control channel segment that does not include user data. The UL traffic channel request module 464 generates a request for traffic channel segments to be allocated, for example, if the WT 400 has user data to convey on the uplink. UL traffic channel tone set determination module 466 determines a set of tones for use corresponding to the assigned uplink traffic channel segment. The set of tones includes multiple tones to be used simultaneously. In the multi-tone mode of operation, even though the WT may be assigned the same WT identifier by the same BS, the logical tone set assigned to the WT to carry uplink traffic channel user data in one time is up at different times. It may be different from the logical tone set assigned to the WT to carry link traffic channel user data. Module 466 can also determine the physical tones corresponding to the logical tones using the tone hopping information. UL traffic channel modulation / coding selection module 468 selects and implements an uplink coding rate and modulation method to be used for the uplink traffic channel segment. For example, in UL multi-tone mode, the WT may support multiple user data rates implemented using different coding rates and / or different modulation methods, eg, QPSK, QAM16. DL traffic channel Ack / Nak module 470 controls Ack / Nak determination and response signaling of the received downlink traffic channel segment while in the uplink multi-tone mode of operation. For example, for each downlink traffic channel segment in the downlink timing structure, the assigned downlink traffic channel segment reverses Ack / Nak carrying the result of the transmission to be used, for example, in the automatic retransmission mechanism. Upon transmission to the BS, there may be a corresponding Ack / Nak uplink segment in the UL multi-tone mode of operation and the uplink timing structure for the WT. The access module 472 controls the access operation, for example, to establish a radio link with a nearby base station, eg, a terrestrial base station and to achieve timing synchronization while in the multi-tone mode of operation. In some embodiments, access module 472 for multi-tone mode has a lower level of complexity than access module 456 for single-tone mode.

Data / information 422 includes uplink mode of operation 474, base station identifier 476, base station system information 475, base station assigned wireless terminal identifier 477, user / device / session / resource information 478. Coded block 482 including uplink user voice data information bits 479, uplink user multiplexed packet data information bits 480, uplink control data information bits 481, uplink user data and control data Coded user data block 483, coded control data block 484, frequency and timing structure information 485, single tone mode coding block information 488, multi-tone mode coding block information 489, single Tone Mode Transmitter Blanking Criteria / Information (490), Single Tone Mode Transmitter Power Adjustment Information (491), Multi-Tone Mode Transmitter Power Adjustment Information (492), and Single Tone Mode Carrier Frequency / Cyclic Extended Adjustment Information Including (493) . The uplink mode of operation 474 may indicate that the WT 400 is currently in a multi-tone uplink mode, for example, to communicate with a terrestrial base station, or, for example, a single-tone to communicate with a satellite base station. It includes information identifying whether it is currently in an uplink mode. BS system information 475 is information associated with each base station in the system, for example, the type of base station, such as satellite or terrestrial, the carrier frequency or frequencies used by the base station, base station identifier information, sector in the base station. For example, timing and frequency uplink and downlink structures used by the base station.

BS identifier 476 includes the identifier of the BS that WT 400 is using as its current network connection point, for example, the identifier of that BS distinguishes the BS from other BSs in the overall system. The BS assigned WT identifier 477 may be an identifier assigned by the BS being used as the network connection point of the WT, and may be, for example, a value in the range of 0,... 31. In the single-tone uplink mode of operation, the identifier 477 may be associated with a single dedicated logical tone in the uplink timing structure to be used by the WT for uplink signaling, including both user data and control data. In the multi-tone uplink mode of operation, the identifier 477 may be associated with a logical tone in the uplink timing structure to be used by the WT for a dedicated control channel for uplink control data. In addition, the BS assigned WT identifier 477 may be used by the BS, for example, when performing segment allocation of uplink traffic channel segments in a multi-tone mode of uplink operation.

User / device / session / resource information 478 includes user and device identification information, routing information, security information, ongoing session information, and air link resource information. Uplink user voice data information bit 479 includes input user data corresponding to the voice call. Uplink user multiplexed packet data information bits 480 include input user data corresponding to, for example, text, video, music, data files, and the like. Uplink control data information bit 481 includes power and timing control information that the WT 400 wants to convey to the BS. Coded block 482 including uplink user data and control bits is a coded output block corresponding to a mixture of user information bits 478 and / or 479 in combination with control information bits 481, and in some embodiments Is formed during UL single tone mode of operation. Coded user data block 483 is a coded block of user information bits 478 and / or 479, while coded control data block 484 is a coded block of control information bits 481. Data and control information are coded separately in the UL multi-tone mode of operation, and in some embodiments, coded separately in the UL single tone mode of operation. In some embodiments of the single-tone mode of operation where coding between uplink user data and uplink control data is separate, the ability to blank the transmitter is facilitated when there is no user data to convey. For example, by not applying output transmitter power on a single uplink tone for some interval dedicated to user data, single tone mode transmitter blanking criteria / information 490 is used in the blanking determination, for example As a result, there is no data to convey because of an interruption of the ongoing conversation. This approach of transmitter blanking results in power savings for wireless terminals and is an important consideration because the average power output is relatively high to facilitate communication with satellites in geostationary orbit. In addition, the level of interference may be reduced.

The single tone mode coding block information 488 may be used to provide the coding rate and modulation method used for the uplink in the single tone mode of operation, e.g., QPSK modulation, which supports at least 4.8 KBit / sec. Includes information identifying the low coding rate to use. The multi-tone mode coding block information 489 is used to uplink traffic channel segments in the uplink during the multi-tone mode of operation to support at least the same coding rate plus some additional higher data rate as in the single tone mode. For a variety of different coding rate and modulation schemes, including a plurality of different data rate options supported, for example QAM4, for example QPSK and QAM16.

Frequency and timing structure information 485 includes dwell boundary information 486 and tone hopping information 487 and corresponds to the BS used as the network connection point. Frequency and timing structure information 485 also includes information identifying logical tones within the timing and frequency structure.

The single tone mode transmitter power adjustment information 491 and the multi-tone mode power adjustment information 492 are, respectively, regarding operation and control of the power amplifier 405 when in the single tone mode and the multi-tone mode of operation. Includes information such as peak power, average power, peak-to-average power ratio, and maximum power level. The single tone mode carrier frequency cyclic extension adjustment information 493 is applied to the symbol boundary in the uplink during the single tone mode of operation, for example, especially during the hop from one physical tone to another physical tone at the dwell boundary. The information used by the dwell boundary and / or inter-symbol boundary carrier coordination module 454 to implement continuity between the signals at.

4 is a diagram 500 illustrating example uplink information bit encoding for an example WT, eg, MN, operating in a single-tone uplink mode of operation, in accordance with various embodiments of the present invention. . In the uplink frequency structure, logical tones are assigned to the WT, either directly or indirectly, for example, by the base station. For example, the BS may assign a user identifier to the single-tone mode WT that may be associated with a specific dedicated logical tone. For example, if the WT is in the multi-tone mode of operation, for example, in general, if the WT carries uplink traffic channel information using seven or more tones at the same time, the logical tone is a dedicated control channel (DCCH). It may be the same logical tone as used as tone. Logical tones may be mapped to physical tones in accordance with tone hopping information known to both the base station and the WT. Tone hopping between different physical tones may occur on a dwell boundary where the dwell may be a fixed number of consecutive OFDM symbol transmission time intervals, eg, seven, in the timing structure used in the uplink. The same logical tone in the uplink frequency structure is used in the single-tone mode of operation, carrying both control information bits 502 and user data information bits 504. The control information bit 502 may include power and timing control information, for example. User data bits 504 may include voice user data information bits 506 and / or multiplexed packet user data bits 508. Multiplexer 510 is used to receive control data information bits 502 and user data information bits 504. Output 512 of multiplexer 510 is an input to uplink block encoding module 514 that encodes a combination of control and user information bits to output coded block 516 of coded bits. The coded bits are mapped to modulation symbols according to the uplink modulation scheme used, e.g., low rate QPSK modulation scheme, and the modulation symbols are transmitted using the physical tone corresponding to the assigned logical tone. The uplink rate is such as to support one or more single voice calls. In some embodiments, the uplink user information rate is at least 4.8 Kbit / sec.

5 is an illustration of an exemplary OFDM wireless multiple access communication system 600 including a hybrid of base stations that are both ground-based and space-based, in accordance with various embodiments of the present invention. Each satellite (satellite 1 602, satellite 2 604, satellite N 606) is a base station (satellite base station 1 608, satellite base station 2 (implemented according to the present invention) and using the method of the present invention. 610, satellite base station N 612. The satellites 602, 604, 606 may be, for example, stationary satellites located in space 601 at about 22,300 mi high earth orbit around the equator of the earth 603. The satellites 602, 604, 606 may each have corresponding cellular coverage areas (cell 1 614, cell 2 616, cell N 618) on the surface of the earth. In addition, the exemplary hybrid communication system 600 includes a plurality of terrestrial base stations, each having a corresponding cellular coverage area (cell 1 '626, cell 2' 628, cell N '630). Ground BS 1 '620, ground BS 2' 622, ground BS N '624). Different cells or portions of different cells may or may not overlap each other partially or completely. Typically, the size of a terrestrial base station cell is smaller than the size of a satellite base station cell. Typically, the number of terrestrial base stations exceeds the number of satellite base stations. In some embodiments, many relatively small terrestrial BS cells are located within relatively large cells of the satellite BS. For example, in some embodiments, terrestrial cells typically have a radius of 1 mi to 5 mi, while satellite cells typically have 100 mi to 500 mi. There are a plurality of wireless terminals implemented in accordance with the invention and using the method of the invention, for example, user communication devices such as cell telephones, PDAs, data terminals and the like. The set of wireless terminals may include stationary nodes and mobile nodes, which may move throughout the system. The mobile node may use the base station as the network connection point of the mobile node in the cell of the base station in which the mobile node currently resides. In some embodiments, terrestrial BSs are used by WTs as the default type of base station to first attempt to use it at a location where access may be provided by either a base station or a satellite base station. It is mainly used to provide access in these areas not covered by the terrestrial base station. For example, in some areas it may not be practical to install terrestrial base stations due to economic, environmental, and / or topographical causes, such as low population density, harsh uninhabitable terrain, and the like. In some terrestrial base station cells, there may be dead spots due to obstacles such as, for example, mountains, tall buildings, and the like. At such dead spot locations, satellite base stations can be used to bridge the gap in coverage, providing a seamless seamless coverage to the WT user. In addition, in some embodiments, priority considerations, and user subscribed tier levels, are used to determine access to satellite base stations. Base stations are coupled together, for example, via a backhaul network and provide interconnection for MNs located in different cells.

MNs in communication with the satellite base station may be operating in a single-tone mode of operation where, for example, a single tone is used for the uplink supporting the voice channel. In the downlink, a larger set of 113 downlink tones received and processed by tones, eg, WT, may be used. For example, in the downlink, the WT may be temporarily assigned a downlink traffic channel segment using multiple tones simultaneously if necessary. The WT may also receive control signaling simultaneously on different tones. Cell 1 614 includes MN 1 632 and MN N 634 in communication with satellite BS 1 608 over wireless links 644, 646, respectively. Cell 2 616 includes MN 1 '636 and MN N' 638 in communication with satellite BS 2 610 via wireless links 648, 650, respectively. Cell N 618 includes MN 1 ″ 640 and MN N ″ 642 in communication with BS N 612 over wireless links 652, 654, respectively. In some embodiments, the downlink between the satellite BS and the MN supports higher rates of user information than the corresponding uplink, eg, supports voice, data, and / or digital video broadcast in the downlink. . In some embodiments, the downlink user data rate provided to the WT using the satellite BS as the network connection point of the WT is approximately equal to the uplink user data rate, eg, 4.8 Kbit / sec, thus, a single voice call. But tends to conserve power sources in satellite base stations.

MNs in communication with terrestrial base stations may operate in a conventional mode of operation, where multiple tones, for example seven or more tones, are used simultaneously for the uplink traffic channel segment. Cell 1 '626 includes MN 1' '' 654 and MN N '' '656 in communication with terrestrial BS 1' 620 via wireless links 666, 668, respectively. . Cell 2 '628 stores MN 1' '' '658 and MN N' '' '660 in communication with terrestrial BS 2' 622 via wireless links 670, 672, respectively. Include. Cell N '630 is MN 1' '' '' 662 and MN N '' '' '664 in communication with terrestrial BS N' 624 via wireless links 674, 676, respectively. )

FIG. 6 is a diagram illustrating an exemplary backhaul interconnection diagram between the various satellite based base stations and various ground based base stations of FIG. 5. Various network nodes 702, 704, 706, 708, 710, 712 communicate with and support satellites via, for example, routers, home agent nodes, external agent nodes, AAA server nodes, and backhaul networks. It may also include satellite tracking / high communication data rate capacity ground stations. The links 714, 716, 718 between the network nodes 702, 712, 708 and satellite base stations 608, 610, 612 functioning as ground stations may be a wireless link using a directional antenna, but the ground node The links between them 720, 722, 724, 726, 728, 730, 732, 734, 736, 738 are wired and / or wireless links, eg, fiber optic cables, broadband cables, microwave links Or the like.

FIG. 7A shows an example satellite 2 604 including an example satellite base station 608 of an example satellite 2 604 and a corresponding cellular coverage area (cell 2) on the surface of the earth. to be. MN 1 636 is located near the center of cell 616 and is closer to satellite 604 than MN N '638 located near the outer periphery of cell 616. In this example, the beam from the satellite covers a large geographic area, and there is a significant difference in round trip time (RTT) (WT-BS-WT) for two different MNs, and MN 1 '636 is Have a shorter RTT. In order to resolve the RTT ambiguity in accordance with the present invention, a range scheme that can resolve several milliseconds of delta-RTT is implemented.

Typically, in a conventional mode of operation, a WT, which may not be precisely timing synchronized or power controlled, may use an uplink tone, for example, to connect and synchronize with a base station and use that BS as the network connection point of the WT. There is a built-in access interval in the timing structure of a system that may transmit a request signal on a contention-based uplink tone. In accordance with various embodiments of the present invention, an access interval for additional time-varying coding on an access tone set to indicate which forward link superslot is associated with a reverse-link transmission, e.g., in a conventional mode of operation. Using the same access interval used, one exemplary way of resolving RTT considerations for one satellite-based tone is disclosed. Such coding can be used to resolve the ambiguity to the superslot level. For example, the superslot may be a duration of about 11.4 msec corresponding to 114 consecutive OFDM symbol transmission time intervals. The wireless terminal may need to attempt repeated access attempts at variable time offsets to cover super-slot (<11,4 msec) ambiguity.

FIG. 8 shows a diagram 800 of an exemplary hybrid system that includes both ground-based and satellite-based base stations, and a wireless terminal that uses terrestrial base station location information to reduce round trip timing ambiguity for satellite base stations. An exemplary WT (MNA) 902 is previously connected to terrestrial BS 2 '622 at cell 2' 628 but moved to cell 2 616 covered by satellite BS 2. MN A 902 seeks to establish a radio link with satellite BS 2 608, but needs to resolve timing ambiguity. In accordance with a feature of the invention, the WT includes information relating the position of the terrestrial base station with the cells of the satellite base station. In some embodiments, multiple terrestrial base stations may be associated with the same satellite cell coverage area (see FIG. 8A). MN A 902 uses the information regarding the location of the last terrestrial base station 622 detected to form an initial RTT estimate. In this way, according to the invention, the ambiguity associated with the RTT can be compressed. In some such embodiments, the ambiguity may be compressed within the range supported by the access protocol used by the terrestrial base station.

8A shows an exemplary embodiment according to the present invention, where multiple base stations are associated with the same satellite coverage area. Although three exemplary base stations are shown for illustrative purposes, a terrestrial BS may typically have a cellular coverage area on the surface of the earth with a radius of about 1 mi to 5 mi, but typically satellites are about 100 mi to 500 mi. Since it may have a cellular coverage area on the surface of the earth at a radius of, it can be seen that there may generally be more terrestrial base stations within or associated with the cellular coverage area of the satellite base station. Terrestrial base stations (BS A 956, BS B 958, BS C 960) having corresponding cells 962, 964, 966 include satellite D 950, which includes satellite BS D 952. Is associated with a coverage area (cell D 954). A wireless terminal attempting to establish a connection with satellite D BS 952, whose exact location is not known, includes known location information of the locations of terrestrial base stations, known locations of satellite base stations in geostationary orbit, and examples. For example, it is possible to estimate the round trip signal time of the wireless terminal based on the signaling information about the terrestrial base stations using the known location of the last terrestrial base station to which the WT was connected as a starting point. For example, the terrestrial BS A 956 located near the outer limit of the cell 954 may correspond to the estimated value representing the longest RTT, and located at an intermediate point between the outer limit of the cell and the center of the cell. The ground BS B 958 may represent an intermediate RTT, but the ground BS C 960 located near the center of the cell 954 may exhibit the shortest RTT.

7 is a flowchart 1200 of an exemplary method of operating a wireless terminal, eg, a mobile node, in accordance with the present invention. The wireless terminal is one of a plurality of first type wireless terminals in an exemplary wireless OFDM multiple access spread spectrum communication system comprising a plurality of base stations, some of which are ground-based base stations and some of which are satellite-based base stations. In this case, the first type wireless terminals can communicate with both the terrestrial base station and the satellite base station. The example communication system may also include example second type wireless terminals capable of communicating with terrestrial base stations but not with satellite base stations.

Operation of the method of flowchart 1200 begins at step 1202 in response to a powered on wireless terminal or in response to a handoff operation. Operation proceeds from start step 1202 to step 1204. In step 1204, the wireless terminal determines whether the network connection point intended to be used as the new network connection point of the wireless terminal is a terrestrial base station or a satellite base station. If it is determined in step 1204 that the new network connection point is a terrestrial base station, operation proceeds to step 1206, where the wireless terminal changes its mode of operation to a first mode of operation, e. Set to link mode. However, if it is determined in step 1204 that the new network connection point is a satellite base station, the operation proceeds to step 1208, where the wireless terminal changes its mode of operation to a second mode of operation, e. Set to tone uplink mode.

Returning to step 1206, the operation proceeds from step 1206 to step 2010 where the WT accepted by the new terrestrial base station receives the base station assigned wireless terminal user identifier. Operation proceeds from step 1210 to steps 1212, 1214, and 1216. In step 1212, the WT is operated to receive a signal from a terrestrial base station corresponding to downlink traffic channel segments carrying downlink user data. Operation proceeds from step 1212 to step 1218, where the WT sends an Acknowledgment / Negative Acknowledgment (Ack / Nak) signal to the base station.

Returning to step 1214, at step 1214, the WT determines a dedicated control channel logical tone from the WT user ID received at step 1212. Operation proceeds from step 1214 to step 1220. In step 1220, the WT determines a physical tone corresponding to the logical tone for use based on the tone hopping information. For example, the WT assigned ID variable may have a range of 32 values (0, ..., 31), each ID uplink including an uplink timing structure, e.g., 113 tones. Corresponds to a different single logical tone in the timing structure. The 113 logical tones may be hopped according to an uplink tone hopping pattern in the uplink timing structure. For example, excluding access intervals, the uplink timing structure may be subdivided into dwell intervals, each dwell interval being a fixed number of durations, e.g., seven consecutive OFDM symbol transmission time intervals. Tone hopping occurs at the dwell boundary rather than in the middle. Operation proceeds from step 1220 to step 1222. In step 1222, the WT is operated to transmit an uplink control channel signal using a dedicated control channel tone.

Returning to step 1216, at step 1216, the WT checks if there is user data to transmit on the uplink. If there is no data waiting to be transmitted, the operation proceeds back to step 1216 where the WT continues to check the data to be transmitted. However, if it is determined in step 1216 that there is user data to transmit on the uplink, the operation proceeds from step 1216 to step 1224. In step 1224, the WT requests uplink traffic channel allocation from the terrestrial base station. Operation proceeds from step 1224 to step 1226. At step 1226, the WT receives an uplink traffic channel segment assignment. Operation proceeds to step 1228, where the WT selects a modulation method to use, such as, for example, QPSK or QAM16. At step 1230, the WT selects a coding rate to be used. Operation proceeds from step 1230 to step 1232, where the WT codes user data for the assigned uplink traffic channel segment according to the selected coding rate of step 1230, and selecting the selected method of step 1228. Map the coded bits to modulation symbol values according to the modulation method. Operation proceeds from step 1232 to step 1234, where the WT determines logical tones to use based on the uplink traffic channel segment assignment. In step 1236, the WT determines physical tones corresponding to logical tones for use based on the tone hopping information. Operation proceeds from step 1236 to step 1238. At step 1238, the WT transmits user data to the terrestrial base station using the determined physical tones.

Returning to step 1208, the operation proceeds from step 1208 to step 1240. In step 1240, the WT accepted by the satellite base station receives the BS assigned WT user ID from the satellite base station. Operation proceeds from step 1240 to step 1242 and step 1244.

In step 1242, the WT is operated to receive signals from the satellite base station corresponding to downlink traffic channel segments carrying downlink user data. Operation proceeds from step 1242 to step 1246, where the WT requests retransmission of downlink traffic channel user data in response to an error. If the downlink transmission has been successfully received and decoded, no response is sent from the wireless terminal to the base station. In some embodiments, if an error is detected in the information recovery process, for example, because the time window of validity for the lost downlink data will expire before the retransmission can be completed or because of the low priority level of the data. However, no request for retransmission is sent.

Returning to step 1244, at step 1244, the WT determines a single uplink logical tone for use with both control data and user data for the assigned WT user ID. Depending on the particular embodiment, the operation proceeds to one of steps 1248 or 1250.

In step 1248, the WT multiplexes the user data and control data to be conveyed over the uplink. The multiplexed data of step 1248 is forwarded to step 1252, where the WT codes a mixture of user and control information bits into a single coded block. Operation proceeds from step 1252 to step 1254 where the WT determines a physical tone for use for each dwell based on the determined logical tone and tone hopping information. Operation proceeds from step 1254 to step 1256. In step 1256, the WT is operated to transmit a coded block of combined user data and control data to the satellite base station, using the determined physical tone for each dwell.

In step 1250, the WT is operated to code user data and control data into independent blocks. Operation proceeds from step 1250 to step 1258, where the WT is operated to determine the physical tone to be used for each dwell based on the determined logical tone and tone hopping information. Operation proceeds from step 1258 to step 1260. In step 1260, the WT is operated to transmit coded blocks of user data and coded blocks of control data to the satellite base station using the determined physical tone determined in units of dwells. Regarding step 1260, in accordance with the features of some embodiments of the present invention, during a time interval dedicated to user data for which there is no user data to be transmitted, a single tone is not used.

Operating the wireless terminal in accordance with the method of flow diagram 1200 is characterized in that multiple OFDM tones are simultaneously used to transmit at least some user data in a first uplink signal having a first peak to average power ratio. It may result in operating the wireless terminal for a first time period comprising a first plurality of consecutive OFDM symbol transmission time periods in a first mode. For example, the WT may be using a terrestrial base station as its network connection point, and may simultaneously use a plurality of tones for uplink traffic channel data, for example, 7, 14, or 28 tones simultaneously. Uplink user data may be conveyed over the air link resource corresponding to the traffic channel segment, and additional tones or tones, eg, dedicated control channel tones, may be used in parallel for control signaling. In addition, operating the wireless terminal in accordance with the method of flow diagram 1200 includes transmitting at least some user data in a second uplink signal having a second peak to average power ratio that is different from the first feed to average power ratio. While at most one OFDM tone is used, it may result in operating the wireless terminal for a second time period comprising a second plurality of consecutive OFDM symbol transmission time periods in a second mode of operation. For example, during a second time period, the WT may be using a satellite base station as its network connection point, and uplink user data through an air link resource corresponding to a single dedicated logical tone associated with the base station assigned WT user identifier. And control data, the single dedicated logical tone may be hopped to different physical tones on a dwell boundary.

In some embodiments, the second peak to average power ratio is less than the first peak to average power ratio, eg, by at least 4 dB. In some embodiments, the WT uses omni-directional antennas. User data delivered on the uplink during a first mode of operation during a first time period may include user data at a rate of at least 4.8 Kbit / sec. User data conveyed on the uplink during the second mode of operation during the second time period may comprise user data at a rate of at least 4.8 Kbit / sec. For example, the voice channel may be supported for WT operation in both the first mode and the second mode of operation. In some embodiments, the WT supports a plurality of different uplink coding options in a first mode of operation, including a plurality of different coding rates and a plurality of different modulation schemes, eg, QPSK, QAM16. In some embodiments, the WT supports a single uplink rate option for operation in the second mode, eg, QPSK using a single coding rate. In some embodiments, the information bit rate for the uplink user data signals in the second mode of operation is below the minimum information bit rate for the uplink user data signal in the second mode of operation.

In some embodiments, if a satellite base station is being used by the WT as a network connection point of a WT, the distance between the satellite base station and the wireless terminal is such that the terrestrial base station is being used by the WT as a network connection point of the WT. At least three times the distance between and the wireless terminal. In some embodiments, at least some of the satellite base stations in the communication system are stationary satellites. In some such embodiments, the distance between the stationary satellite base station and the WT using that base station as the network connection point of the WT is at least 35,000 km, but the distance between the ground station and the WT using that ground station as the network connection point of the WT is at most 100. km. In some embodiments, the satellite base station being used by the WT as a network connection point of the WT is at least a distance from the WT such that the signal round trip time exceeds 100 OFDM symbol transmission time periods, each OFDM symbol transmission time. The period includes the amount of time used to transmit one OFDM symbol and the corresponding cyclic prefix.

In some embodiments, switching from the first mode of operation to the second mode of operation occurs when a handoff occurs between a terrestrial base station and a satellite base station. In some such embodiments in which switching from the first mode of operation to the second mode of operation has occurred, the WT stops sending acknowledgment signals in response to the received downlink user data. In some such embodiments where switching from the first mode of operation to the second mode of operation has occurred, the WT reduces the frequency and / or the number of uplink control signals to be transmitted.

Other embodiments in accordance with various aspects of the present invention include systems that include satellite-based base stations but do not include ground-based base stations, systems that include terrestrial base stations, but do not include satellite-based base stations, and airborne platform-based systems. It may include various combinations including a base station.

In various embodiments of the present invention, when a portion of the base station communicates with a remote base station using multiple tones in the uplink, a UL assignment to be adjusted to resolve the allocation of traffic segments> 2 x maximum RTT (round trip time) Uplink segment allocation is used by the slave architecture. Extreme link budget requirements for successful reception of a transmission signal by a satellite base station, in some but not all cases, of terminals without high gain antennas, for example, a handset with an omni-directional antenna or an almost omni-directional antenna. May restrict communication through the use of a single work mode. Thus, in some embodiments, when a handoff from a terrestrial base station to a satellite base station occurs, the wireless terminal detects the change and switches from multi-tone uplink mode to single OFDM tone uplink mode operation.

For stationary satellites with a beam covering a large geographic area, there may be a significant difference in round trip time between the center and the edge of the beam. To resolve this RTT ambiguity, a range scheme that can resolve several milliseconds of delta-RTT may be desirable.

Such a scheme may use the existing access interval in OFDM for additional time-varying coding on the access tone set to indicate which forward link superslot is associated with the reverse-link transmission. Such coding may resolve the ambiguity to the superslot level. The terminal may need to attempt repeated access attempts at variable time offsets to cover sub-superslot (<11.4 msec) ambiguity. In a hybrid terrestrial-satellite network, the terminal may use the information about the location of the last terrestrial base station detected to form an initial RTT estimate and compress the ambiguity within the range supported by the general access protocol.

9 is a diagram 1000 illustrating that the round trip signal delay between the satellite base station and the WT located above the ground is greater than the superslot. The diagram 1000 includes a horizontal axis 1002 representing time, the access probe signal 1004 is transmitted from a ground terminal located at the ground to a satellite base station, and the response signal 1006 from the satellite base station is located at ground level. Received by the wireless terminal. Round trip delay time 1008 is greater than the super-slot time interval. For example, in some terrestrial wireless communication systems, an access interval is configured once in every superslot that provides the opportunity for the wireless terminal to request and establish timing synchronization with a new terrestrial BS. For ground-based wireless terminals seeking access to terrestrial base stations, where the round trip distance is relatively short, typically 2 miles to 10 miles, the round trip signal travel time is between about 11 micro-seconds and 54 The round trip delay, which is micro-seconds and includes signal processing by the terrestrial base station, may be in a super-slot, for example, the time interval of 114 super-slots represents about 11.4 msec. Thus, there is no ambiguity about what superslots the access probes and response signals are associated with. On the other hand, for a terrestrial wireless terminal seeking access to a satellite base station in a stationary orbit of about 22,300 mi with a round trip signal travel time of about 240 msec, the round trip delay will be greater than the super-slot interval time of 11.4 msec. In addition, there may be a change in round trip delay due to the large coverage area of the satellite base station resulting in different RTT depending on the position of the WT in the cell. Thus, according to the present invention, there is no access method of the WT that seeks to establish a radio link with the satellite BS and to synchronize the timing when the WT seeks to connect to the terrestrial BS and that the WT connects to the satellite BS. If so, it is modified to resolve existing timing ambiguity issues.

FIG. 10 is a diagram 1100 illustrating one aspect of the invention used in an access process to determine timing synchronization between a satellite base station and a WT. FIG. 10 shows that the exemplary timing structure is subdivided into superslots, eg, 114 OFDM symbol time intervals, and the beginning of each superslot is an access interval, eg, 9 OFDM symbol time intervals. do. The diagram 1100 includes a horizontal axis 1102 representing time, superslot 1 1104, superslot 2 1106, superslot N 1108. Superslot 1 1104 includes an exemplary terrestrial access interval 1110, superslot 2 1106 includes an exemplary terrestrial access interval 1112, and superslot N is an exemplary terrestrial access interval 1114. It includes. The base station may transmit a reference signal, eg, a beacon signal defining a beacon slot, and the superslots may be indexed within the beacon slot. With respect to the terrestrial BS, the WT seeking to establish a link with the BS transmits an access probe signal during the access interval, and the BS receiving the signal may send back a WT identifier and timing correction to provide synchronization. However, for satellite BS, the timing ambiguity is greater than that of the superslot. Thus, the WT may code the access signal probe differently depending on the superslot that was transmitted. The coded access probe signal 1116 that occurs within the access interval 1110 is coded to identify superslot 1 1104. The coded access probe signal 1118 that occurred during the access interval 1112 is coded to identify superslot 2 1106. The coded access probe signal generated during the access interval 1114 is coded to identify superslot N 1108. Thus, when the base station receives a coded access probe signal, the BS can determine from that code the superslot that was transmitted.

FIG. 11 is a diagram 1200 illustrating another aspect of the invention used in an access process to determine timing synchronization between a satellite base station and a WT. FIG. 11 shows, from the WT's perspective, that the WT will offset the access probe signal, eg, by different offsets, eg, 400 micro-second offset, so that the satellite can further resolve timing synchronization into the superslot. Shows that it can. The diagram 1200 includes a horizontal axis 1150 representing time, superslot 1 1152, superslot 2 1154, and superslot N 1156. Superslots 1152, 1154, 1156 are time intervals 1158, 1160, 1162 that are typically used by the WT to provide an opportunity for the WT to transmit an access probe signal to the ground base station to establish a connection and timing synchronization. ), For example, nine OFDM symbol transmission time intervals at the beginning of each superslot. When operating in a mode for attempting access with a satellite base station, the WT is accessed at different times, including, for example, a time outside the intervals 1158, 1160, 1162 within the superslot relative to the criteria of the WT. Probes can be sent. Access probe signals 1164, 1166, 1168, 1170, 1172, 1174, 1176 are shown with exemplary spacing offsets between the access probe signals that are 400 micro-seconds, with the access probe occurring at various times within the superslot. Indicates that it may. The access probe signals transmitted during superslot 1 1152, for example, the access probe signal 1164, 1166, 1168, 1170 or 1172 are coded to identify superslot 1. Access probe signals transmitted during superslot 2 1154, such as access probe 1174, are coded to identify superslot 2. Access probe signals transmitted during superslot N 1156, such as access probe 1176, are coded to identify superslot N.

WTs located on the ground that are not tightly synchronized to the satellite base station and where there is a large degree of uncertainty due to the large possible distance change between the satellite and the WT are short intervals in the superslot, e.g. the interval used by the terrestrial base station. It is possible to monitor the access probe signals from the WT during the same interval corresponding to. If the transmitted WT probe signal does not hit the access interval window of opportunity for reception at the satellite base station, the satellite base station will not decode the request. The WT can make up for potential changes in timing by sending multiple requests with different offsets, and eventually the WT probe signal must be captured and decoded by the satellite BS. The satellite BS can then identify the superslot to which the signal was guided by decoding the signal and resolve the timing into the superslot, and the satellite BS can transmit the BS assigned WT identifier and timing correction signal to the WT. . The WT may apply the received timing correction information to synchronize with the satellite base station.

12 further illustrates the concept of a WT transmitting multiple access probes to a satellite base station at different timing offsets. FIG. 12 is a diagram 1169 including a horizontal axis 1171 indicating a time period in which the WT transmits access probes to a satellite base station. 12 shows a first superslot used by the WT to transmit the access probe signal 1175 while the WT transmits the coded access probe signal 1177 according to the first timing offset value T ₀ 1179, A second superslot used by the WT to transmit the access probe signal 1180 while the WT transmits the coded access probe signal 1182 according to the second timing offset t ₀ + DELTA 1184, and the Nth timing An Nth superslot used by the WT to transmit the access probe signal 1186 while the WT transmits the coded access probe signal 1188 according to the offset value t ₀ + NDELTA 1190. Assume that the satellite BS will accept one of the access probes that occurs to be within the access interval monitored by the BS for receiving and processing access probe signals from the WTs, eg, the k th probe.

For example, assume that the ambiguity in timing between the satellite BS and the terrestrial WT is greater than the superslot. The WT seeks to connect to the satellite BS. The satellite BS outputs beacon signals, each beacon signal associated with a set of beacon slots and superslots. Each superslot has an access interval, e.g., 9 OFDM symbols, in which the BS accepts coded access probes from the WT seeking to establish a connection with the satellite BS. From the perspective of the BS receiving the signal, if the access probe is outside this access interval window, the BS will not accept the signal. The WT, which uses the satellite BS as the network connection point of the WT, transmits a coded access probe signal that is coded to indicate the super-slot index number. Since the WT access probe may be outside of the receiving window when it reaches the BS, the WT may send multiple probes at different timing offsets, eg, with respect to the start of the superslot. For example, a timing offset of 400 micro-seconds may be used. For example, the WT may transmit a sequence of access probes, eg, 10 access probes, at intervals of about 1/2 second, with each successive access probe having a different timing offset with respect to the start of the superslot. However, the BS will only accept access probe signals received within its access interval window. Access probe signals outside that window are allowed by the system as interference noise. When the BS receives an access probe of one of the multiple access probes from the WT received within the access interval window, the BS determines the superslot information by decoding the signal and achieves timing synchronization between the BS and the WT. To determine the timing correction. The BS sends the base station assigned WT identifier, repetition of superslot identification information, and timing correction value to the WT. The WT may receive the base station assigned WT identifier and apply timing correction to thereby use the satellite BS as the network connection point of the WT. The single dedicated logical uplink tone may be associated with an assigned WT identifier for the WT for use for uplink signaling to the satellite BS.

13 is a diagram 1300 illustrating exemplary access signaling in accordance with the method of the present invention. 13 includes an exemplary base station 1302 and an exemplary wireless terminal 1304 implemented in accordance with the present invention. Example BS 1302 transmits downlink signaling using downlink timing and frequency structure. The downlink timing structure includes beacon slots, each beacon slot including a fixed number of indexed superslots, eg, eight indexed superslots per beacon slot, each superslot fixed A number of OFDM symbol transmission time intervals, eg, 114 OFDM symbol transmission time intervals per superslot. In addition, each beacon slot includes a beacon signal. Downlink signals from BS 1302 are received by WT 1304, and the downlink signaling delay between when BS 1302 transmits and when WT 1304 receives is determined by the distance between BS and WT. Change as a function The received beacon signal 1306 corresponds to the corresponding superslots (Superslot 1 1310, Superslot 2 1312, Superslot 3 1314, ..., Superslot N 1316). Is shown as a beacon slot 1308. The WT 1304 may reference uplink signaling regarding received beaconslot timing.

BS 1302 also maintains the uplink timing and frequency structure synchronized at the base station with respect to the downlink timing structure. Within the uplink timing and frequency structure at BS 1302, there is a receive window that receives access signals, for example, one window may be provided for each superslot 1318, 1320, 1322, ..., 1324. )

The WT 1304 sends an uplink access probe signal 1326 to the BS 1302 to seek to acquire and register access with the BS 1302 to the BS 1302. Arrows 1328, 1330, 1332 indicate propagation delays (shorter, medium, and longer) corresponding to (short, medium, and long) distances between BS 1302 and WT 1304, respectively. In this case, (A, B, C) is shown.

In an example case A, the WT 1304 sends an access probe signal 1326, which successfully hits the access window 1318 of opportunity. BS 1302 can process the access probe signal, determine a timing offset, and send a timing offset correction to WT 1304, wherein uplink signals from WT 1304 can, for example, perform data communication. In order to arrive in synchronization with BS 1302 at the uplink reception timing, allowing the WT 1304 to use the received timing offset correction to adjust the uplink transmission timing to more precisely time synchronize its uplink signaling. do.

In example case B, the WT 1304 sends an access probe signal 1326, which misses the access windows 1318, 1320 of opportunity. BS 1302 does not successfully process its access probe signal, and the access probe signal is treated as interference by BS 1302 and BS 1302 does not respond to WT 1304.

In example case C, the WT 1304 sends an access probe signal 1326, which successfully hits the access window 1320 of opportunity. BS 1302 can process the access probe signal, determine a timing offset correction, and send the timing offset correction to WT 1304, wherein the uplink signals from WT 1304 can be, for example, data. To allow the WT 1304 to adjust the uplink transmission timing in order to more accurately timing its uplink signaling, to reach in synchronization with the BS 1302 at the uplink reception timing that allows communication. To use.

For example, in some embodiments of a near base station, such as a terrestrial BS with a cell radius of 5 miles, the amount of round trip time uncertainty is relatively small, and when transmitting an access probe uplink signal, the WT 1304 at the base station It can be expected to hit the next access window. In some embodiments, if the base station is spaced far from the WT but the relative distance uncertainty is very small, the access probe signal can be expected to hit the access window at the base station.

However, in embodiments where the uncertainty in the round trip time is greater than that supported by the access interval size, the access probe signal may or may not hit the access window of opportunity. In such a case, if the access probe misses as in case B above, the WT timing is adjusted and another access probe needs to be sent. The access interval window time represents signaling overhead and it is desirable to keep the access interval short. For example, an example access window time interval is nine OFDM symbol transmission time intervals corresponding to 114 OFDM symbol transmission time intervals of an exemplary superslot.

In the examples of FIG. 13, the propagation delay such that the access probe signal 1326 can hit different access windows 1318, 1320 depending on, for example, the relative distance between the WT 1304 and the BS 1302. It should be observed that there may be a change in. For example, the relative distance of the BS to the WT may vary so that, if successfully received, the access probe signal may be received in different of the access windows depending on the relative BS-WT distance at a given time. Assume that case A (arrow 1328) and case C (arrow 1332) correspond to the BS. Also assume that the WT is allowed to transmit access probe signals during superslots with different index values. When the BS receives an access probe signal to calculate the correct timing correction, the base station needs to know more information from the WT 1304 to obtain a timing reference point. According to one aspect of some embodiments of the invention, the WT codes the access probe signal 1326 to identify the superslot index from which the access probe signal 1326 was transmitted. BS 1302 uses the slot index information to calculate timing offset correction that is sent to WT 1304 on the downlink signal. The WT 1304 receives the timing correction signal and adjusts its uplink timing accordingly.

In some embodiments of the invention, the access probe signal does not code a superslot index, but the base station distinguishes the access window 1318 and the access window 1320 to indicate a timing correction signal and a slot index offset, for example. Another way of passing the ruler on the downlink is used. Then, the WT 1304, knowing the superslot index of the transmitted access probe signal, combines the received timing correction signal and the received slot index indicator and its information to calculate the composite timing adjustment and apply the timing adjustment. can do.

14 is a diagram 1400 illustrating exemplary access signaling in accordance with the method of the present invention. 14 includes an example base station 1402 and an example wireless terminal 1404 implemented in accordance with the present invention. Exemplary BS 1402 transmits downlink signaling using downlink timing and frequency structure. The downlink timing structure includes beacon slots, each beacon slot including a fixed number of indexed superslots, eg, eight indexed superslots per beacon slot, each superslot fixed A number of OFDM symbol transmission time intervals, eg, 114 OFDM symbol transmission time intervals per superslot. In addition, each beacon slot includes a beacon signal. Downlink signals from BS 1402 are received by WT 1404, and the downlink signaling delay between when BS 1402 transmits and when WT 1404 receives is determined by the distance between BS and WT. Change as a function The received beacon signal 1406 corresponds to the indexed superslots (Superslot 1 1410, Superslot 2 1412, Superslot 3 1414, ..., Superslot N 1416). Is shown as beacon slot 1408. The WT 1404 may refer to uplink signaling regarding received beaconslot timing. There is an RTT uncertainty that may or may not be successful when the WT 1404 hits an access slot at the base station 1402 when transmitting an access probe signal.

BS 1402 also maintains the uplink timing and frequency structure synchronized at the base station with respect to its downlink timing structure. Within the uplink timing and frequency structure in BS 1402, there are receive windows that receive access signals, i.e., access slots, for example, one window is a respective superslot 1418, 1420, 1422. , ..., 1424). In addition, the uplink timing is configured such that data slots 1426, 1428, 1430 exist between access slots.

14 illustrates a method of adjusting access probe timing offsets relative to the start of a superslot such that an access probe uplink signal is eventually received in an access slot, in accordance with the present invention. The method is useful if there is a change in signal RTT, for example due to a potential change in BS-WT distance, such that hitting the access window is not guaranteed in the first attempt.

The WT 1404 transmits an access probe signal 1432, and the transmission timing is controlled such that there is a first timing offset, ie, timing offset t ₁ 1434, relative to the start of the superslot from which the signal is transmitted. The transmitted access probe signal 1432 is an uplink signal that is delayed by signaling propagation and arrives as an access probe signal 1432 ′ at the receiver of the BS 1402 as indicated by the oblique arrow 1433. However, access probe signal 1432 'occurs to arrive during data slot 1426, and is therefore considered to be interference by BS 1402. BS 1402 does not send a response to WT 1404.

The WT 1404 adjusts its timing offset to the second timing offset value t ₂ 1438, and transmits an access probe signal 1434. The transmitted access probe signal 1436 is an uplink signal that is delayed by signaling propagation and arrives as an access probe signal 1436 ′ at the receiver of the BS 1402 as indicated by the oblique arrow 1437. However, this time of the received access probe signal 1434'is present in the access slot 1420, and the BS 1402 processes the access signal, accepts the WT 1404 to be registered, and receives a timing correction signal. The timing correction signal is calculated and transmitted to the WT 1404 on the downlink. The WT adjusts its uplink timing in accordance with the received timing correction signal.

The difference between the access probe signaling timing offsets may be selected in correlation to the size of the access slot such that successive access probes with different offsets eventually hit the access slot. For example, in an example system having access slots of nine OFDM symbol transmission time intervals, different time offsets may be different by four OFDM symbol transmission time intervals, for example, the OFDM transmission time interval is about 100 microns. -Seconds.

15 is a diagram 1500 illustrating exemplary access signaling in accordance with the method of the present invention. 15 includes an example base station 1502 and an example wireless terminal 1504 implemented in accordance with the present invention. Assume that example BS 1502 may be a satellite BS in geostationary orbit having a large cellular coverage area, eg, 100, 200, 500 or more miles on the earth's surface. In such an embodiment, for example, the potential WT 1504 may be such that the RTT is greater than the superslot in the downlink and the example access probe signal may or may not hit an access time slot at the base station 1500. Assume that there is an RTT uncertainty due to a change in position. In this exemplary embodiment, the two characteristics described above that code the superslot index identification information into the access probe and transmit successive access probes with different timing offsets from the start of the superslot from which the access signal is transmitted, are described in WT ( Used in combination to obtain timing correction for 1504).

BS 1502 transmits downlink signals including downlink beacon signals per beacon slot that are part of a downlink timing structure that includes superslots, the downlink timing structure being known to BS and WT. The WT 1504 may synchronize with respect to the received downlink signal and may identify the index value of the superslots within each beacon slot.

WT 1504 decides to use BS 1502 as a network connection point, ie, a satellite BS, but WT 1504 does not know its location and therefore does not know the RTT. The WT 1504 sends an access probe signal 1508 with a first timing offset t ₁ 1510 about the start of the superslot 1512 where the signal is transmitted. The index number of the superslot 1512 in the beaconslot of the superslot 1512 is known to the WT 1504 and encoded in the access probe signal 1508. After the WT-BS propagation delay time, the access signal arrives at BS 1502 as an access probe 1508 '. However, the access probe signal 1508 'hits the data slot 1514 rather than the access slot. BS 1502 treats signal 1508 'as interference and does not respond to WT 1504.

The wireless terminal 1504 waits a time interval 1516 before sending another access probe signal. The time interval 1516 is chosen to be greater than the additional time allowed for RTT plus signal processing, where the access probe signal has successfully hit the access slot at BS 1502 and BS 1502 has registered the WT 1504 for registration. ) Provides enough time for the BS 1502 to generate, transmit, propagate an access probe response signal, and to be detected by the WT 1504.

If no response was received at the expected time interval, the WT 1504 adjusts the timing offset of that WT from the start of the superslot with a second timing offset 1518 that is different from the first timing offset 1510, Send another access probe signal 1520 during superslot 1522. The index number of superslot 1522 in the beacon slot of superslot 1522 is coded at signal 1520, and the index value may be the same or different than the index value coded at signal 1508. After the WT-BS propagation delay time, the access signal arrives at BS 1502 as an access probe 1520 '. In this case, the access probe signal 1520 'hits the access slot 1521. BS 1502 decodes the passed superslot index, measures the received signal 1520 'timing offset within access slot 1521, and uses the measured timing offset and superslot information to WT 1504. Calculate the timing correction for BS 1502 sends the timing offset correction value to WT 1504 as a downlink signal. The WT 1504 receives and decodes the timing offset value and adjusts its uplink timing according to the received correction. Signaling that identifies that the WT 1504 is accepted for registration by the BS 1502, for example, before the time that the WT 1504 attempts to transmit another access probe signal with a different offset, for example. Received.

16 is a flowchart 1600 of an exemplary method of operating a wireless terminal to access a base station and perform a timing synchronization operation, in accordance with the present invention. Operation begins in start phase 1602, where the WT is powered on and initialized and begins to receive downlink signals from one or more base stations. Operation proceeds from step 1602 to step 1604.

In step 1604, the WT determines whether to seek to initiate access with a satellite or terrestrial base station. Exemplary WT implemented in accordance with the present invention may include implementation of different methods of access. The first method of access is tailored to a satellite base station, e.g., a satellite base station in geostationary orbit having a cell coverage area on the surface of the earth with a radius of about 100 mi to 500 mi, where the signal RTT is greater than the superslot. However, the ambiguity in the RTT is greater than the access time interval. The second method of access is, for example, tailored to a terrestrial base station with a relatively small cell radius, for example 1, 2, or 5 mi, where the signal RTT is smaller than the superslot and the ambiguity in the RTT is For example, the access request signal sent from the WT is small enough to be expected to hit the access slot in the terrestrial BS in a single attempt. If the WT is attempting to access the satellite BS, operation proceeds from step 1604 to step 1606, but if the WT seeks to access a terrestrial base station, operation proceeds from step 1604 to step 1608. Proceed.

At step 1606, the WT is operated to receive a downlink beacon signal or signals from the satellite BS. The downlink timing and frequency structure used by the satellite base station in the example system may include periodically occurring beacon slots, each beacon slot including a beacon signal, and each beacon slot being a fixed number of Superslots, for example eight superslots, each superslot in the beaconslot is associated with an index value, and each superslot is a fixed number of OFDM symbol transmission time intervals, for example 114 OFDM symbol transmission time intervals.

Operation proceeds from step 1606 to step 1608. In step 1608, the WT determines a timing reference from the received beacon signal (s) and, for example, determines the start of a beacon slot on the received downlink signaling. In step 1610, the WT sets the probe counter equal to 1, and in step 1612, the WT sets the timing offset variable equal to the initial timing offset, for example, the initial timing offset is set to WT. Is a predetermined value stored. Operation proceeds from step 1612 to step 1614.

In step 1614, the WT selects a superslot within the beaconslot to transmit the first access probe signal and identifies the index of the selected superslot. Then, at step 1614, the WT codes the index of the selected superslot into the first access probe signal. Next, at step 1618, the WT transmits a first access probe signal at a point in time that occurred within the selected superslot such that the transmission is a timing offset from the start of the selected superslot by the timing offset value of step 1612. Operation proceeds from step 1618 to step 1622 via the access node A 1620.

In step 1622, the WT is operated to receive downlink signaling from the satellite base station, the received downlink signaling may include a response to the access probe signal. Operation proceeds from step 1622 to step 1624. At step 1624, the WT checks to see if it has received a response directed to that WT. If no response has been received, the operation proceeds from step 1624 to step 1626, but if a response directed to the WT is received, the operation proceeds to step 1628.

In step 1626, the WT checks whether the change in time since the last access probe transmission exceeded the expected worst-case RTT + processing time, eg, a predetermined limit stored in the WT. If the time limit has not been exceeded, the operation returns to step 1622 where the WT continues the process of receiving the downlink signal and checking the response. However, at step 1626, if the WT determines that the time limit has been exceeded, the WT operation proceeds to step 1630, where the WT increments the probe counter.

Next, at step 1632, the WT checks whether the probe counter exceeds the maximum number of probe counters. The maximum number of probe counters may be any value stored in the WT memory selected such that the maximum number of probe counters with different timing offsets is sufficient to cover the timing ambiguity so that one or more of the access probes can be located at the satellite base station. It is expected to be timed to hit the access slot.

If the probe counter in step 1632 exceeds the maximum number of probes, it can be assumed that the set of access attempts will fail, and operation proceeds to step 1604 via access node B 1634. For example, a possible cause of failure is WT access due to interference conditions, such as loading considerations, that prevent an access probe signal that must hit an access slot at a base station cannot be successfully detected and processed. May include a response signal from the satellite base station, or the satellite base station, which has been determined to reject the &lt; RTI ID = 0.0 &gt; At step 1604, the WT may determine whether to repeat the process for the same satellite base station or to attempt to access a different base station.

If the probe counter does not exceed the maximum number of probe counters in step 1632, operation proceeds to step 1636, where the WT sets the timing offset equal to the current timing offset value plus delta offset. For example, the delta offset may be a fraction that is less than half the access slot interval, for example. Then, at step 1640, the WT selects a superslot within the beaconslot to transmit another access probe signal, and identifies the index of the selected superslot. Next, at step 1641, the WT codes the index of the selected superslot into another access probe signal. The WT then transmits another access probe signal at a point in time that occurred within the selected superslot, such that at step 1644, the transmission is a timing offset from the start of the selected superslot by the timing offset of step 1638. Operation proceeds back from step 1644 to step 1622 via access node A 1620, where the WT receives the downlink signals and checks the response to the access probe signal.

Returning to step 1624, if it is determined in step 1624 that the WT has received a response directed to the wireless terminal, the operation proceeds to step 1628, where the WT includes timing correction information to the WT. Process the received response that is guided. Operation proceeds from step 1628 to step 1646. In step 1646, the WT adjusts the WT timing information in accordance with the received timing correction information.

Returning to step 1604, in step 1604, if the wireless terminal seeks to initiate access via the terrestrial BS, the operation proceeds to step 1608, where the WT is the WT as its network connection point. Operate to receive a downlink beacon signal or signals from a terrestrial base station desired to use. Then, in step 1646, the WT determines a timing reference from the received beacon signal or signals, and in step 1648, the WT uses the determined timing criteria to ensure that the access request signal is received at the terrestrial base station during the access interval. Determine the time to transmit the access request signal to be expected to be received. Operation proceeds from step 1648 to step 1650.

In step 1650, the WT is operated to transmit an access request signal at a determined time, which does not include coded superslot identification information. Next, at step 1652, the WT is operated to receive downlink signaling from a terrestrial BS that may include access grant information. Operation proceeds from step 1652 to step 1654.

At step 1654, the WT is operated to determine whether the WT has received an access grant signal in response to its access request signal. If no access grant has been received, the operation proceeds from access node B 1634 from step 1654, where the WT retries access with the same terrestrial base station or attempts access with a different BS. Determine. If at step 1654 it is determined that the WT is granted access to use the terrestrial BS as its network connection point, the operation proceeds to step 1656, where the WT includes timing correction information and is directed to the WT. Operate to process the grant signaling. Then, at step 1658, the WT is operated to adjust the WT timing according to the received timing correction information of step 1656.

17, which includes a combination of FIGS. 17A and 17B, is a flowchart 1700 of an example method of operating a communications device for use in a communications system. For example, the example communication device may be a wireless terminal, such as a mobile node implemented in accordance with the present invention, and the example communication system may be a multiple access spread spectrum OFDM wireless communication system. The communication system may include one or more base stations, and each base station may transmit downlink beacon signals. The various base stations in the system may or may not be timing synchronized with each other. In an example communication system, beacon signaling broadcast by a base station may be used in providing timing reference information about the base station. In an exemplary communication system, a timing structure for a base station exists such that a beacon time slot occurs periodically, and the beacon signal is transmitted by the base station during each beacon time slot in accordance with a periodic downlink timing structure, the downlink The timing structure includes a plurality of superslots in each beacon slot, and individual superslots in each beacon slot are suitable for identification through the use of a superslot index, each superslot for a plurality of symbol transmission time intervals. Include.

Operation begins in start step 1702, where the communication device is powered up and initialized. Operation proceeds from step 1702 to step 1704. In step 1704, the communication device receives one or more beacon signals from a base station, for example, a satellite BS, that the communication device wants to use as a network connection point. In some embodiments, the communication system receives multiple beacon signals and / or other downlink broadcast information, eg, pilot signals, from base stations prior to processing. Operation proceeds from step 1704 to step 1706. In step 1706, the communication device processes the received beacon signal to determine the downlink timing reference point, wherein the superslots occur within the beacon slot having a predetermined reference to the determined timing reference point. Operation proceeds from step 1706 to step 1708.

In step 1708, the communication device determines a time to transmit the first access probe as a function of the determined timing reference point. For example, the first access probe has an initial time offset from the determined timing reference point. In some embodiments, for example, in some hybrid systems including both satellite base stations and terrestrial base stations, the communication device performs sub-step 1709, and in sub-step 1709, the communication device is from the terrestrial base station. Determine a time to transmit the first access probe as a function of the location information determined from the signal of. In some such embodiments, determining the time to transmit the first access probe is further performed as a function of known information indicative of the location of the terrestrial base station and the location of the satellite base station. For example, the base station that the communication device currently wishes to transmit an access probe signal to may be a satellite base station, and a relatively large in timing to use to transmit the access probe due to a relatively large change in signal RTT due to the large coverage area on the earth's surface. Positive uncertainties may exist and the current location of the communication device is unknown. However, a cell coverage area of a satellite that overlaps with or is in proximity to a number of smaller cells may include smaller cells corresponding to the satellite base station. By approximating the current location of the communication device determined from terrestrial base station signals, the communication device may reduce timing uncertainty regarding when to transmit the access probe, thus increasing the likelihood that the access probe will be accepted by the satellite base station. And reduce the time and number of different timing access probes that need to be sent to the satellite BS. For example, a communication device may store information identifying the last terrestrial BS that communication device used as an access point, and information correlating satellite location and / or satellite cell location with terrestrial BS cells may also be stored and used. It may be. In some embodiments, the communication device may triangulate the location of the device based on beacon signals received from the plurality of terrestrial base stations. In some embodiments, it may be possible to reduce the level of timing uncertainty by using location information derived from terrestrial base stations in order for a first access probe for a satellite base station to be expected to hit the access slot of that satellite base station. .

Operation proceeds from step 1708 to step 1710. At step 1710, the communication device codes the information in the first access probe signal that identifies the first superslot index. Then, in step 1712, the communication device transmits a first access probe signal identifying the first superslot index, where the first access probe signal is a first for the start of the first superslot index. Is sent at a timing offset. Operation proceeds from step 1712 to step 1714, where the communication device monitors to determine whether a response to the first access probe signal has been received from the base station. Then, at step 1716, operation proceeds to step 1718 if no response has been received, or to step 1720 if a response has been received.

If a response has been received, at step 1720, the communication device performs transmission timing adjustment as a function of the information included in the response.

However, if a response has not been received, at step 1718, the communication device codes the information in the second access probe signal identifying the second superslot index, and at step 1722, the communication device is assigned a second superslot. Transmit a second access probe signal identifying the second superslot index at a second timing offset with respect to the start of a second superslot with an index, the second timing offset being different than the first timing offset. Operation proceeds from step 1722 to step 1726 via connection node A 1724.

At step 1726, the communication device monitors to determine whether a response to the second access probe signal has been received from the base station. Then, in step 1728, operation proceeds to step 1732 if no response is received, or operation proceeds to step 1730 if a response is received.

If a response has been received, at step 1732, the communication device performs transmission timing adjustment as a function of the information included in the response.

However, if a response has not been received, at step 1730, the communication device codes the information in the third access probe signal identifying a third superslot index, and at step 1734, the communication device is assigned to the third super. Transmit a third access probe signal at a third timing offset with respect to the start of the third superslot with the slot index, the third timing offset being different than the second timing offset.

Operation proceeds from step 1734 to step 1736. In step 1736, the communication device monitors to determine whether a response to the third access probe signal has been received from the base station. Then, at step 1738, operation proceeds to step 1742 if no response is received, or operation proceeds to step 1740 if a response is received.

If a response has been received, at step 1742, the communication device performs transmission timing adjustment as a function of the information included in the response. If no response has been received, at step 1740, the communication device continues with the process of generating / sending / responding decision / additional action according to the embodiment. For example, in some embodiments, the communication device may deliver access probes with different timing offsets for each successive access probes until it responds to the probe or until a fixed number of access probes are sent. have. For example, the total number of access probes may be at least sufficient to cover the expected timing ambiguity.

In some embodiments, the first and second access probes are transmitted in different beacon slots, and the second superslot index is the same or different than the first superslot index. In some embodiments, the first and second access probes are transmitted in different beacon slots, and the second superslot index is different from the first superslot index.

In some embodiments, the first and second access probes are transmitted in the same beaconslot, and the second superslot is different from the first superslot. In some such embodiments, the response includes information identifying one of the probe signals to be answered.

In some embodiments in which a sequence comprising three or more access probes is transmitted, the second timing offset is different from the first timing offset by the sum of the initial timing offset value and the first integer multiple of the fixed step size offset, and the third The timing offset differs by the sum of the initial timing offset value and the second integer multiple of the fixed step size timing offset, and the second integer multiple of the fixed step size timing offset differs from the first integer multiple of the fixed step size offset. In some embodiments, the first and second integer multiples of the fixed step size timing offset can be either positive or negative.

In some embodiments, the fixed step size is less than the duration of the base station access interval, where the base station access interval is a period of time during which the base station responds to the access probe signal.

In various embodiments, the base station to which the communication device sends the access probe is a satellite base station, and for a signal traveling at the speed of light, the round trip time (RTT) between the satellite base station and the communication device is greater than the duration of the superslot. In some such embodiments, the RTT is also greater than the duration of the beaconslot. In some embodiments, the RTT is greater than 0.2 seconds.

18 is a flowchart 1800 of an example method of operating an example communications device in accordance with the present invention. An exemplary method of flow diagram 1800 is a method of operating a communication device for use in a communication system in which a beacon time slot occurs periodically, wherein the beacon signal is a base station during each beacon time slot according to a periodic downlink timing structure. And the downlink timing structure includes a plurality of superslots in each beacon slot, wherein individual superslots in the beacon slot are suitable for identification through the use of a superslot index, each superslot Symbol transmission time periods.

Operation begins in step 1802, where the communication device is powered on and initialized. Operation proceeds from step 1802 to step 1804, where the communication device is operated to receive one or more beacon signals, and then, in step 1806, the communication device processes and receives the received beacon signal down. The link timing reference point is determined, and the superslots occur within a beaconslot having a predetermined relationship to the determined timing reference point. Operation proceeds from step 1806 to step 1808.

In step 1808, the communication device codes the access probe identifier in one or more of the first and second access probes. In step 1810, the communication device transmits a first access probe at a time corresponding to the first timing offset relating to the start of the superslot in the beaconslot. Then, in step 1812, the communication device transmits a second access probe at a time corresponding to the second timing offset with respect to the start of the superslot, from which point the first access probe was transmitted, the larger superslot The second access probe is transmitted at a time that is less than a duration and twice the time required for the transmission signal to move from the communication device to the base station. Operation proceeds from step 1812 to step 1814.

At step 1814, the communication device is operated to be monitored to determine whether a response has been received from the base station, and at step 1816, the operation proceeds based on the determination. If a response was received from the base station, operation proceeds from step 1816 to step 1818. In step 1818, the communication device performs transmission timing adjustment as a function of the information included in the response. If a response has not been received from the base station, operation proceeds from step 1816 to step 1804 via access node A 1820, where the communication device can restart the process of initiating access signaling.

In some embodiments, the maximum timing ambiguity is less than the duration of the superslot and the time between the transmission of the first access probe and the transmission of the second access probe is less than the duration of the superslot. In some embodiments, the first and second access probes are transmitted at intervals from each other that are less than or equal to the access interval at which the base station will respond to receiving access probes.

In various embodiments, wherein the received response includes information identifying the access probe to which the response corresponds, performing the transmission timing adjustment as a function of the information contained in the response includes: timing correction information received from the base station; Determining an amount of timing adjustment to be performed from information about the transmission time of the identified probe with respect to the determined downlink timing reference point.

19 is a flow chart 1900 of an example method of operating an example communication device in accordance with the present invention. An example method of flow diagram 1900 is a method of operating a communication device for use in a communication system where a beacon time slot occurs periodically, e. Transmitted by a base station, e. Suitable for identification through a channel, each superslot includes a plurality of symbol transmission time periods.

Operation begins in step 1902, where the communication device is powered on and initialized. Operation proceeds from step 1902 to step 1904, where the communication device operates to receive one or more beacon signals from a base station, and then, in step 1906, the communication device processes the received beacon signal. Downlink timing reference point, and superslots occur within a beaconslot having a predetermined relationship to the determined timing reference point. Operation proceeds from step 1906 to step 1908.

In step 1908, the communication device is operated to transmit an access probe signal to a base station. Then, in step 1910, a response to the access probe signal is received from the base station, the response being i) an amount of the indicated main superslot timing offset correction, which is an integer multiple of the superslot time period, and ii) receiving And information indicating one or more of the superslot identifiers indicating the positions of the superslots in the beacon slots that the base station has received the access probe signal corresponding to the response. Operation proceeds from step 1910 to step 1912, where the communication device performs timing adjustment as a function of the received information in the received response. Step 1912 includes sub-step 1914. In sub-step 1914, the communication device determines a timing adjustment amount from information received from the base station and information indicating the time at which the access probe signal was transmitted.

In some embodiments, the received response from the base station includes a superslot identifier indicative of the location of the superslot in the beacon slot from which the base station received the access probe signal, and adjusts transmission timing adjustment as a function of the information contained in the response. Performing includes determining a main superslot timing offset from the superslot identifier included in the received response, and information indicating the superslot location relative to the downlink timing reference point in the beaconslot from which the access probe was sent; The main superslot timing offset is an integer multiple of the duration of the superslot. In some such embodiments, the received response further includes sub-superslot timing correction information comprising a sub-superslot time offset, and performing the transmission timing adjustment includes determining the determined main superslot timing offset and the sub-superslot. Adjusting the transmission timing by an amount corresponding to the sum of the time offsets.

In various embodiments, the received response from the base station is a sub-superslot timing indicating a main superslot timing offset that is an integer multiple of the duration of the superslot and a sub-superslot time offset that is a time offset less than the duration of the superslot. Contains correction information. In some embodiments, performing the transmission timing adjustment includes adjusting the transmission timing by an amount corresponding to the sum of the main superslot timing offset and the sub-superslot time offset. In some such embodiments, the main superslot timing offset and sub-superslot time offset are delivered as part of a single coded value. In another embodiment, the main superslot timing offset and the sub-superslot time offset are delivered as two separately coded values.

20 is a flowchart 2000 of an exemplary method of operating a wireless communication terminal in a system having a downlink timing structure comprising a plurality of superslots that cycle in a periodic manner. Operation begins in step 2002, where the wireless terminal is powered on and initialized. Operation proceeds from step 2002 to step 2004, where the wireless terminal is operated to determine whether the base station to which the wireless terminal seeks to transmit uplink signals is a satellite base station or a terrestrial base station. . Based on the determination of step 2004, the operation proceeds from step 2006 to either step 2008 for a satellite BS or step 2010 if the base station is a terrestrial base station.

In step 2008, the wireless terminal is operated to perform a first uplink timing synchronization process, the first uplink timing synchronization process supporting delivery of an uplink timing correction signal to the communication terminal. Step 2008 includes sub-steps 2012, 2014, and 2016. In a sub-step 2012, the wireless terminal is operated to transmit an access probe signal to a satellite base station. In step 2014, the wireless terminal is operated to receive a response from the base station in response to the access probe signal, the response being i) an amount of indicated main superslot timing offset correction that is an integer multiple of the superslot time period, and ii) receiving. The response includes one or more of the superslot identifiers indicating the positions of the superslots in the beacon slots where the base station has received the corresponding access probe signal. Then, in step 2016, the wireless terminal performs transmission timing adjustment as a function of the information included in its received response.

In step 2010, the wireless terminal performs a second uplink timing synchronization process that is different from the first timing synchronization process. Step 2010 includes sub-steps 2018, 2020, and 2022. In sub-step 2018, the wireless terminal transmits an access probe signal to a terrestrial base station. In step 2020, the wireless terminal receives a response from the terrestrial base station in response to the access probe signal, the response including information indicating a timing correction that is less than the duration of the superslot. In some embodiments, the timing correction is less than the duration of the access interval. In some embodiments, the timing correction is less than half the duration of the access interval. Then, in step 2022, the wireless terminal performs transmission timing adjustment as a function of the information included in the response received from the terrestrial base station, which adjusts the transmitter timing by an amount less than the duration of the superslot. Related to that.

21 is a diagram of an exemplary wireless terminal 2100, eg, a mobile node, implemented in accordance with the present invention. Exemplary WT 2100 may be used in various embodiments of the wireless communication system of the present invention. The example WT 2100 includes a receiver 2102, a transmitter 2104, a processor 2106, and a memory 2108 coupled together via a bus 2110 in which various elements may exchange data and information. Include. The memory 2108 includes a routine 2120 and data / information 2122. The processor 2106, eg, the CPU, executes routines in the memory 2108 and uses the data / information 2122 to control the operation of the WT 2100 and implement the methods of the present invention.

The receiver 2102, eg, an OFDM receiver, is coupled to a receive antenna 2112 on which the WT 2100 can receive downlink signals from the base station, including beacon signals and response signals including timing adjustment information. do. The transmitter 2104, eg, an OFDM transmitter, is coupled to a transmit antenna 2116 on which the WT 2100 can transmit uplink signals including access probe signals to a base station. The timing of the access probe signal, including the offset from the superslots, the superslot to transmit a given access probe signal and the beaconslot, is controllable at the transmitter 2104. Receiver 2102 includes a decoder module 2114 used to decode downlink signals, while transmitter 2104 includes an encoder module 2118 for encoding uplink signals.

The routine 2120 includes a communication routine 2124 for implementing the communication protocol used by the WT 2100, and a WT control routine 2125 for controlling the operation of the WT 2100. The WT control routine 2125 is configured to receive the received signal processing module 2126, coding module 2128, transmitter control module 2130, monitoring module 2132, timing correction module 2134, decoder module 2136, and location. Based timing adjustment module 2138. The received signal processing module 2126 processes the signals including the beacon signals and determines a downlink timing reference point from the one or more beacon signals. In some embodiments, coding module 2128 operating alone or in conjunction with encoder 2118 codes the information in the access probe signal that identifies a superslot index corresponding to the access probe signal. In some embodiments, the WT identifier and / or unique access probe identifier is coded and included in the access probe signal. Transmitter control module 2130 operates to control operations of transmitter 2104 that include controlling coded access probe signals to be transmitted at a timing offset, eg, a different timing offset for different access probes. In some embodiments, transmitter control module 2130 controls the transmission of consecutive access probes to be greater than twice the signaling time plus signal processing time from the WT to the base station, eg, another access probe. Allow the WT 2100 to observe whether it responds to the access probe before issuing the. The monitoring module 2132 is used to determine whether a response to the access probe signal is received from the base station. The timing correction module 2134 responds to the monitoring module 2132 and performs transmission timing adjustment as a function of the information included in the received access probe response. Decoder module 2136, operating alone or in conjunction with decoder 2114, decodes information in a response that identifies one of the access probe signals. The location based timing adjustment module 2138 determines the time to transmit the first access probe as a function of location information determined from the signal received from the terrestrial base station. Location-based timing adjustment module 2138 may be used to reduce timing ambiguity associated with satellite base stations due to large coverage areas, thus reducing the number of access probes needed and / or the average time of an access process by satellite base stations. .

Data / information 2122 may include timing / frequency structure information 2140, user / device / session / resource information 2142, a plurality of access probe signal information sets (first access probe signal information 2144,... ., N-th access probe signal information 2146), received beacon signal information 2148, timing reference point information 2150, initial timing offset information 2152, step size information 2154, received response signal information 2156, timing adjustment information 2158, and terrestrial BS / satellite BS location information 2160. Timing / frequency structure information 2140 is a grouping of OFDM symbol transmission time intervals such as downlink and uplink timing and frequency structure information, periodicity information, index information, OFDM symbol transmission time interval information, slots, superslots, beacon slots, and the like. Information about, base station identification information, beacon signal information, repetitive interval information, access interval information, uplink carrier frequency, downlink carrier frequency, uplink tone block information, downlink tone block information, uplink and downlink tone hopping Information, base station identification information, and the like. Timing / frequency structure information 2140 includes information corresponding to a plurality of base stations that may exist in a wireless communication system. The user / device / session / resource information 2142 may correspond to information corresponding to the user of the WT 2100 and, for example, identifiers, addresses, routing information, for example downlink traffic channel segments, by terrestrial base stations. Communication with WT 2100, including assigned air link resources such as uplink traffic channel segments for multi-tone mode, single dedicated logical tones for uplink signaling by satellite BS, base station assigned WT user identifiers, and the like. Contains information corresponding to a peer in the session. The first access probe information 2144 includes information corresponding to the access probe, for example, timing offset information regarding the start of the superslot, information identifying a superslot index, coded information, information identifying a beacon slot, and the like. Include. The N-th access probe information 2146 may include timing offset information corresponding to an access probe, for example, information about a start of a superslot, information identifying a superslot index, coded information, information identifying a beacon slot, and the like. Include. Different sets of access probe information 2144, 2146 may partially or completely include different information, eg, different timing offsets, different superslot index values or different timing offsets, same superslot index values. . In addition, access probe signal information 2144, 2146 may include user identification information, such as a WT user identifier and / or a unique access probe signal identifier, and tone information associated with the access probe signal. Received beacon signal information 2148 may be configured to provide information from the received beacon signal, for example, information relating to a particular base station, carrier frequency, and / or sector and beacon, beacon signal strength information, and a WT timing reference point. Information such as to establish such information. Timing reference point information 2150 includes information determined using, for example, downlink beacon signaling to establish a beaconslot start on which a reference point, eg, superslot index, is based. The access probe signaling transmission timing may be referenced with respect to the established timing reference point information 2150. Initial timing offset information 2152 includes information identifying, for example, an initial timing offset value used in the calculation of a timing offset relating to the start of a superslot for access probes. Step size information 2154 includes information identifying a fixed step size timing offset that is added to the initial timing offset by an integer multiple to determine the offset from the start of the superslot for the particular access probe, for example, different Access probes use different integer multiples of the step size timing offset. In some embodiments, the fixed step size is less than the duration of the base station access interval, where the base station access interval is a period of time during which the base station responds to access probe signals. Received response signal information 2156 includes information received in response to access probe signaling including timing correction information. Timing correction information may be coded. In some embodiments, response signal information 2156 also includes information identifying which of the access probe signals is answered, eg, via a WT identifier and / or a unique access probe signal identifier. The timing adjustment information 2158 includes timing correction information extracted from the received response signal, and information indicating changes to transmission timing as a result of applying the correction information. Terrestrial base station / satellite base station position information 2160 includes information indicative of the position of terrestrial base stations and the position of satellite base stations in the system. Information 2160 may also include information that correlates cell coverage areas or satellite base stations with terrestrial base stations.

23 is a diagram of an exemplary wireless terminal 2300, eg, a mobile node, implemented in accordance with the present invention. Exemplary WT 2300 may be used in various embodiments of the wireless communication system of the present invention. The example WT 2300 includes a receiver 2302, a transmitter 2304, a processor 2306, and a memory 2308 coupled together via a bus 2310 through which various elements may exchange data and information. Include. The memory 2308 includes a routine 2320 and data / information 2232. Processor 2306, eg, a CPU, executes routines in memory 2308 and uses data / information 2322 to control the operation of WT 2300 and implement the methods of the present invention.

The receiver 2302, for example an OFDM receiver, is coupled to a receive antenna 2312 where the WT 2300 can receive downlink signals from the base station, including beacon signals and response signals including timing adjustment information. do. Transmitter 2304, for example, an OFDM transmitter, is coupled to transmit antenna 2316, through which WT 2300 can transmit uplink signals including access probe signals to a base station. The timing of the access probe signal, including the offset from the superslots, the superslot and the beaconslot to transmit a given access probe signal are controllable at the transmitter 2304. Receiver 2302 includes a decoder module 2314 that is used to decode downlink signals, while transmitter 2304 includes an encoder module 2318 for encoding uplink signals.

The routine 2320 includes a communication routine 2324 for implementing the communication protocol used by the WT 2300, and a WT control routine 2325 for controlling the operation of the WT 2300. The WT control routine 2325 includes a received signal processing module 2326, a coding module 2328, a transmitter control module 2330, a monitoring module 2332, a timing adjustment module 2334, and a decoder module 2336. do. The received signal processing module 2326 processes the signals including the beacon signals and determines a downlink timing reference point from the one or more beacon signals. In some embodiments, coding module 2328, operating alone or in conjunction with encoder 2318, codes information in an access probe signal that identifies, for example, a corresponding access probe signal within a sequence of access probe signals. . In addition, the wireless terminal identifier and / or the unique access probe signal identifier may be encoded to allow for discrimination between a plurality of WTs in a system that may transmit access probes. Transmitter control module 2330 operates to control operations of transmitter 2304 including controlling coded access probe signals to be transmitted at a timing offset, eg, a different timing offset for different access probes. In some embodiments, the time between successive access probes may be less than the duration of the larger superslot and twice the time required for the signal to move from the WT to the base station. For example, suppose a superslot contains one access interval, but the timing ambiguity is less than the superslot duration but may be greater than the access interval, and the WT is smaller than the access interval to cover the possible timing range ambiguity within the superslot. A sequence of coded access probes may be transmitted, eg, to identify the access probe spaced apart by a time interval. The monitoring module 2332 is used to determine whether a response to the access probe signal is received from the base station. Timing adjustment module 2334 responds to monitoring module 2332 and performs transmission timing adjustment as a function of information included in the received access probe response. Decoder module 2336, operating alone or in conjunction with decoder 2314, decodes information in a response that identifies one of the access probe signals.

The data / information 2322 includes timing / frequency structure information 2340, user / device / session / resource information 2234, a plurality of access probe signal information sets (first access probe signal information 2344),... , N-th access probe signal information 2346), received beacon signal information 2348, timing reference point information 2350, access probe interval / offset information 2352, received response signal information 2356, And timing adjustment information 2358. Timing / frequency structure information 2340 is a grouping of OFDM symbol transmission time intervals such as downlink and uplink timing and frequency structure information, periodicity information, index information, OFDM symbol transmission time interval information, slots, superslots, beacon slots, and the like. Information about, base station identification information, beacon signal information, repetitive interval information, access interval information, uplink carrier frequency, downlink carrier frequency, uplink tone block information, downlink tone block information, uplink and downlink tone hopping Information, base station identification information, and the like. Timing / frequency structure information 2340 includes information corresponding to a plurality of base stations that may exist in a wireless communication system. The user / device / session / resource information 2234 may correspond to information corresponding to the user of the WT 2300 and, for example, identifiers, addresses, routing information, e.g., downlink traffic channel segments, by terrestrial base stations. Communication with WT 2300, including assigned air link resources such as uplink traffic channel segments for multi-tone mode, single dedicated logical tones for uplink signaling by satellite BS, base station assigned WT user identifiers, and the like. Contains information corresponding to peers in the session. The first access probe information 2344 may include, for example, timing offset information regarding the start of a superslot, information identifying a superslot index, coded information, information identifying a beacon slot, and the like corresponding to the access probe. Include. N-th access probe information 2346 may include, for example, timing offset information regarding the start of a superslot, information identifying a superslot index, coded information, information identifying a beacon slot, and the like corresponding to the access probe. Include. Different sets of access probe information 2344, 2346 may partially or completely include different information, eg, the same superslot but different timing offset. In addition, access probe signal information 2344 and 2346 may include user identification information, such as a WT identifier and / or a unique access probe signal identifier, and tone information associated with the access probe signal. Received beacon signal information 2348 provides information from the received beacon signal, e.g., information relating to a particular base station, carrier frequency, and / or sector and beacon, beacon signal strength information, WT to a timing reference point. Information such as to establish such information. Timing reference point information 2350 includes information determined using, for example, downlink beacon signaling to establish a beaconslot start on which a reference point, eg, superslot index, is based. The access probe signaling transmission timing may be referenced with respect to the established timing reference point information 2350. Access probe interval / offset information 2352 includes timing information about access probes in a sequence of access probes, eg, a delta time interval between successive access probes. For example, if each access interval duration is less than the superslot but timing ambiguity is greater than the access interval duration, the number of consecutive access probes may be spaced apart by a delta time interval that is less than or equal to the access interval duration, and the number is A number for covering the timing ambiguity range. Received response signal information 2356 includes information received in response to access probe signaling including timing correction information. Timing correction information may be coded. In some embodiments, response signal information 2356 also includes information identifying whether one of the access probe signals in the sequence of consecutive access probes is answered. The timing adjustment information 2358 includes timing correction information extracted from the received response signal, and information indicating changes to transmission timing as a result of applying the correction information. In addition, the received response signal information 2356 may include a WT identifier and / or a unique access probe signal identifier.

24 is a diagram of an exemplary wireless terminal 2400, eg, a mobile node, implemented in accordance with the present invention. The example WT 2400 may be used in various embodiments of the wireless communication system of the present invention. Exemplary WT 2400 includes a receiver 2402, a transmitter 2404, a processor 2406, and a memory 2408 coupled together via a bus 2410 through which various elements may exchange data and information. Include. The memory 2408 includes a routine 2420 and data / information 2422. The processor 2406, eg, the CPU, executes routines in the memory 2408 and uses the data / information 2422 to control the operation of the WT 2400 and implement the methods of the present invention.

The receiver 2402, for example, an OFDM receiver, is coupled to a receive antenna 2412 in which the WT 2400 can receive from the base station downlink signals including response signals and beacon signals including timing adjustment information. do. Transmitter 2404, eg, an OFDM transmitter, is coupled to a transmit antenna 2416 that the WT 2400 can transmit uplink signals including access probe signals to a base station. The timing of the access probe signal, including the offset from the superslots, the superslot and the beaconslot to transmit a given access probe signal are controllable at the transmitter 2404. Receiver 2402 includes a decoder module 2414 that is used to decode downlink signals, while transmitter 2404 includes an encoder module 2418 for encoding uplink signals.

The routine 2420 includes a communication routine 2424 for implementing the communication protocol used by the WT 2400, and a WT control routine 2425 for controlling the operation of the WT 2400. The WT control routine 2425 includes a received signal processing module 2426, a coding module 2428, a transmitter control module 2430, a monitoring module 2432, a transmission timing adjustment module 2434, and a receiver control and decoding module. (2436). The received signal processing module 2426 processes the signals including the beacon signals and determines a downlink timing reference point from the one or more beacon signals. Coding module 2428, operating alone or in conjunction with encoder 2418, codes information in uplink signals and, for example, a WT identifier and / or in an access probe signal to be transmitted by WT 2400. It encodes a unique access probe identifier, and those identifiers cause the access probe to be distinguished by the BS from other access probes that may be transmitted by other WTs. Transmitter control module 2430 controls the operation of transmitter 2404 including controlling access probe signals to be transmitted at a timing offset, eg, a different timing offset from the start of the superslot for the different access probes. It works. In some embodiments, the transmitter control module 2430 controls the transmission of consecutive access probes to be greater than twice the signaling time plus signal processing time from the WT to the base station, and for example, another access probe. Allow the WT 2400 to observe whether or not responding to the access probe before issue. The monitoring module 2432 is used to determine whether a response to the access probe signal is received from the base station. The transmission timing adjustment module 2434 is responsive to the monitoring module 2432 and performs transmission timing adjustment as a function of the information included in the received access probe response signal. For example, the transmission timing adjustment module 2434, along with information known to the WT 2400 as to when the access probe was transmitted, includes information in the received response signal, eg, sub-superslot timing offset. The timing adjustment may be calculated using the correction information 2464 and either a superslot position indicator or a main superslot timing offset correction value indicative of reception at the base station. In some embodiments, the received response signal carries sub-superslot timing offset information, eg, through coded bits in the response signal, and the main superslot timing offset information carries through the transmission time of the response signal. do. In some embodiments, receiver control and decoder module 2436, operating alone or in conjunction with decoder 2414, receives an access probe response signal from a base station, i) the indicated main superslot, which is an integer multiple of the superslot time period. And information in the response extracting one or more of an amount of timing offset correction, and ii) a superslot identifier indicative of the location of the superslot in the beacon slot that the base station received the access probe signal corresponding to the received response. In some embodiments, the main superslot timing offset is coded by the sub-superslot time offset as a single coded value, and module 2436 performs the decoding operation. In some embodiments, the main superslot timing offset is coded separately from the sub-superslot time offset as two separately coded values, and module 2436 performs a decoding operation. In some embodiments, the sub-slot timing offset is carried through the coded bits of the response signal, and the main superslot offset is carried through controlling the transmission time of the response signal, eg, the response signal offset by a different amount. do. In some embodiments, the response signal may be a WT identifier and / or a unique access probe signal identifier 2465 such that the WT 2400 may acknowledge that the response signal is directed to a WT 2400 rather than another WT in the system. ) Is also included.

Data / information 2422 includes timing / frequency structure information 2440, user / device / session / resource information 2442, a plurality of access probe signal information sets (first access probe signal information 2444),... ., N-th access probe signal information 2446), received beacon signal information 2448, timing reference point information 2450, initial timing offset information 2452, step size information 2454, received response signal information 2456, and timing adjustment information 2458. Timing / frequency structure information 2440 is a grouping of OFDM symbol transmission time intervals such as downlink and uplink timing and frequency structure information, periodicity information, index information, OFDM symbol transmission time interval information, slots, superslots, beacon slots, and the like. Information about, base station identification information, beacon signal information, repetitive interval information, access interval information, uplink carrier frequency, downlink carrier frequency, uplink tone block information, downlink tone block information, uplink and downlink tone hopping Information, base station identification information, and the like. Timing / frequency structure information 2440 includes information corresponding to a plurality of base stations that may exist in a wireless communication system. The user / device / session / resource information 2442 may correspond to information corresponding to the user of the WT 2400 and, for example, identifiers, addresses, routing information, e.g., downlink traffic channel segments, by terrestrial base stations. Communication with WT 2400, including assigned air link resources such as uplink traffic channel segments for multi-tone mode, single dedicated logical tones for uplink signaling by satellite BS, base station assigned WT user identifiers, and the like. Contains information corresponding to peers in the session. The first access probe information 2444 includes, for example, timing offset information regarding the start of a superslot, information identifying a superslot index, information identifying a beacon slot, and the like corresponding to the access probe. N-th access probe information 2446 includes, for example, timing offset information regarding the start of a superslot, information identifying a superslot index, information identifying a beacon slot, and the like corresponding to the access probe. Different sets of access probe information 2444, 2446 may partially or completely include different information, eg, different timing offsets, different superslot index values or different timing offsets, the same superslot index values. In addition, access probe signal information 2444 and 2446 may include user identification information, such as a WT identifier and / or a unique access probe signal identifier, and tone information associated with the access probe signal. The WT identifier and / or the unique access probe signal identifier may be encoded into an access probe signal so that the BS can distinguish a plurality of access probes from different WTs in the system, for example, and the BS may include a WT ( 2400 may include identification in the response signals that inform the response signal to the WT 2400. Received beacon signal information 2448 may include information from the received beacon signal, e.g., information relating to a particular base station, carrier frequency, and / or sector and beacon, beacon signal strength information, WT to a timing reference point. Information such as to establish such information. Timing reference point information 2450 includes information determined using, for example, downlink beacon signaling to establish a beaconslot start on which a reference point, eg, superslot index, is based. The access probe signaling transmission timing may be referenced with respect to established timing reference point information 2450. Initial timing offset information 2452 includes information identifying, for example, an initial timing offset value used in the calculation of a timing offset relating to the start of a superslot for access probes. Step size information 2454 includes information identifying a fixed step size timing offset that is added to the initial timing offset by an integer multiple to determine the offset from the start of the superslot for the particular access probe, for example, different Access probes use different integer multiples of the step size timing offset. In some embodiments, the fixed step size is less than the duration of the base station access interval, where the base station access interval is a period of time during which the base station responds to access probe signals. Received response signal information 2456 includes information received in response to access probe signaling including timing correction information. The received response signal information 2456 may be a WT identifier and / or a unique access probe signal identifier 2465 that allows the WT 2400 to acknowledge that the response signal is directed to a WT 2400 rather than another WT in the system. ) May be included. In some embodiments, the response signal information 2456 is sent to the WT 2400 if the WT 2400 transmits a plurality of access probes at a time interval that is less than twice the signal transmission time from the WT to the BS, for example. It also includes information identifying which of the access probe signals transmitted by the device is answered. Timing correction information may be coded. In some embodiments, response signal information 2156 also includes information identifying which of the access probe signals is answered. The received response signal information 2456 is sub-superslot timing offset correction information 2464, and in some embodiments, the main superslot timing offset correction information 2460, which is, for example, an integer multiple of the superslot time period, And, for example, one or more of superslot location identifiers 2246 identifying the location of the superslot in the beaconslot where the base station received the corresponding access probe signal with the received response. The timing adjustment information 2458 indicates the timing correction information extracted from the received response signal, and changes in transmission timing as a result of applying the correction information in combination with, for example, known timing information corresponding to the access probe. Contains information.

22 illustrates a method of operating a base station, eg, a satellite base station, in accordance with an exemplary embodiment of the present invention. All or part of the method may be used depending on the particular embodiment and the type of wireless terminal signaling transmitted to the base station, eg, the type of information encoded with respect to transmitted access probes.

The method begins, for example, at step 2202 where the base station is initialized and placed in operation. The operation proceeds along the parallel path to step 2203 and step 2204, which may be performed in parallel. In step 2203, the base station transmits beacon signals periodically according to a given downlink timing structure, and one or more beacon signals are transmitted during each beacon slot. In various embodiments, the beacon signal is a signal transmitted at a higher power level than commonly used to transmit user data, eg, text, video or application data. In some embodiments, the beacon signal is a narrowband signal. In some embodiments, the beacon signal is implemented as a single tone signal transmitted for several consecutive symbol transmission time periods, eg, less than three or four consecutive OFDM symbol time periods. Beacon signals are transmitted periodically as determined by the downlink timing structure.

In step 2204, which may occur in parallel with the beacon transmission step 2203, the base station monitors, for example, during an access interval that occurs periodically, to detect access probe signals. In some embodiments, the periodic access interval has a duration shorter than the period of the downlink superslot. The access probe signals may be received from one or more communication devices that have not yet fully achieved uplink timing synchronization with the base station. Superslot and / or sub-superslot uplink timing correction may be required before wireless terminals transmitting access probes achieve symbol level uplink timing synchronization with the base station. For each access probe signal detected in step 2204, the operation proceeds to step 2206. In step 2206, the base station determines an index of the downlink superslot time period at which the access probe signal was received. This may be different from the superslot in which the transmitting communication device is believed to have transmitted the access probe. The determination of in which downlink superslot the access probe signal was received may be made using internal base station timing information and information regarding when the access probe was received.

Operation proceeds from step 2206 to step 2208. In step 2208, the base station performs a decoding operation on the access probe signal such that the signal, for example, an access probe identifier, a communication device identifier identifying a transmitting communication device, and / or a transmitting device, for example Detects information that may be encoded with respect to a downlink superslot identifier that indicates the index of the superslot in the beacon slot that sent the access probe.

Regarding the access probe information to be decoded, the operation proceeds to step 2210 and 2212. In step 2210, the base station serves to be performed by a communication device transmitting a received probe to achieve appropriate symbol level timing within the superslot for signals transmitted to that base station, e.g., OFDM symbols. Determine the superslot uplink transmission timing correction offset. This timing correction value is a value representing a correction smaller than the duration of the superslot. Operation proceeds from step 2210 to step 2214.

Step 2212 is an operational step performed in some embodiments where the superslot index is encoded with respect to the received access probe. In step 2212, which is not necessarily all embodiments, but performed in some embodiments, the main superslot timing offset correction is accessed as indicated by the decoded superslot identifier and the determined index of the downlink superslot from which the access probe was received. It is determined from the difference between the indices of the superslots where the probes were sent. Operation proceeds from step 2212 to step 2214.

Step 2214 is a step in which a response to the received access probe is generated and transmitted. In some embodiments, the response is transmitted in a downlink superslot with a predetermined downlink superslot offset from the downlink superslot time period in which the access probe to which the response was received was received by the base station. The superslot offset is sufficient for the base station to process and generate one or two superslot in from the superslot where the required response, e.g., the access probe was received. One such embodiment in which responses are sent in a downlink superslot with a predetermined known superslot offset from the superslot from which the response was received, causes the wireless terminal to estimate the superslot timing offset error from the response timing.

In some embodiments in which the access probe response signals transmit a response at a predetermined superslot offset relative to when the access probe was received, the wireless terminal receiving the access probe response,

Main timing adjustment = 2x (index of the superslot at which the response to the access probe was received-index of the superslot determined by the communication device to which the access probe was sent)-fixed superslot delay) x period of the superslot

The main timing adjustment to be implemented is performed according to the following equation. The fixed superslot delay is a function of some offset. A multipler of two considers that the associated delay is a round trip delay, but the multiplication of the number of cycles of the downlink superslot takes into account the duration of the superslots.

In step 2214, the sub-superslot uplink timing offset correction determined in step 2210 is encoded in the response. In addition, other information may also be encoded with the generated access probe response signal. Each element may, for example, be coded separately as separate error values, or may be combined with main and sub-superslot error information to be coded as a single value, for example. In sub-step 2224, the main superslot uplink timing offset correction, e.g., the correction value generated in step 2212, is coded into a response signal. In sub-step 2226, the superslot identifier indicating the index of the downlink superslot from which the access probe signal was received is encoded into the response signal. In sub-step 2228, the communication device identifier and / or access probe identifier corresponding to the receiving access probe to be answered is encoded into a response signal. Identification of the communication device to which the response is directed may be useful in a multi-user system in which multiple devices may generate requests, in particular, as part of a contention based access process. Operation proceeds from step 2214 to step 2230, where the generated probe is transmitted as an access probe response signal. Processing corresponding to the detected receive access probe stops at step 2232, but reception and processing of other access probes may continue.

25 is a diagram of an exemplary base station 2500, eg, satellite based base station, implemented in accordance with the present invention and using the method of the present invention. Example base station 2500 may be a BS in an example wireless communication system implemented in accordance with the present invention. Since the base station provides network access to the WTs, the base station 2500 is often referred to as an access node. The base station 2500 includes a receiver 2502, a transmitter 2504, a processor 2506, and a memory 2508 coupled together via a bus 2510 in which various elements may exchange data and information. . Receiver 2502 includes a decoder 2512 for decoding received uplink signals from WTs, including, for example, access probe signals. Transmitter 2504 includes an encoder 2514 for encoding downlink signals to be transmitted, for example, to WTs including downlink response signals and downlink beacon signals for access probes. Each of receiver 2502 and transmitter 2504 is coupled to antennas 2516, 2518, where uplink signals are received from WTs and downlink signals are transmitted to WTs, respectively. In some embodiments, the same antenna is used for receiver 2502 and transmitter 2504. In addition to communicating with the WTs, the base station 2500 can communicate with other network nodes. In some embodiments where the BS 2500 is a satellite BS, the BS communicates with a ground station having a directional antenna and a high capacity link, which ground station is connected to other network nodes, eg, other base stations, routers, AAA servers. , Home agent nodes and the Internet. In some such embodiments, the same receiver 2502, transmitter 2504 and / or antenna described above with respect to the BS-WT communication link are used for the BS-network node ground station link, but in other embodiments, separate elements are Used for different functions. In an embodiment where BS 2500 is a terrestrial base station, BS 2500 includes a network interface that couples the BS 2500 with other network nodes and / or the Internet. The memory 2508 includes a routine 2520 and data / information 2522. The processor 2506, eg, the CPU, executes the routine 2520 in the memory 2508 and uses the data / information 2522 to control the operation of the base station 2500 and implement the method of the present invention.

The memory 2508 includes a communication routine 2524 and a base station control routine 2526. Communication routine 2524 implements various communication protocols used by base station 2500. Base station control routine 2526 includes a scheduler module 2528, a transmitter control module 2530, a receiver control module 2536, an encoder module 2546 that assigns segments, eg, downlink traffic channel segments, to WTs. An access probe decoding and processing module 2548, and a timing correction determination module 2550.

The transmitter control module controls the operation of the transmitter 2504. Transmitter control module 2530 includes a beacon module 2532 and an access probe response module 2534. The beacon module controls the transmission of beacon signals, eg, transmission of one or more beacon signals during the beaconslot. In some embodiments, the beacon signal is a single tone signal. In some embodiments, the beacon signal has a duration less than three OFDM symbol transmission time periods. The access probe response module 2534 controls the generation and transmission of response signals in response to the access probe signals.

Receiver control module 2536 includes access probe reception and detection module 2540. Receiver control module 2536 controls receiver 2502 operation. The access probe reception and detection module 2540 is used in receiving and detecting access probe signals from wireless terminals. The access probe detection module 2540 includes an access probe detection module 2542 and an access time interval determination module 2544. The access time interval determination module 2544 identifies a predetermined periodic time period that occurs during a portion of each superslot during the beacon slot, wherein the portion is less than half of the superslot, and the predetermined time period receives the access probes. Often referred to as an access interval or slot that is reserved for. Access probes arriving outside the access interval are treated as interference by the base station and are not answered. In some embodiments, the access interval is less than 25% of the superslot interval. For example, the access interval may be 8 or 9 OFDM transmission time intervals corresponding to superslots of 114 OFDM symbol transmission time intervals. In some embodiments, the OFDM symbol transmission time interval is about 100 micro-seconds. The access probe detection module 2252 detects and processes received access probes that have arrived during the time interval deemed acceptable by the access time interval determination module 2544.

In some embodiments, encoder module 2546, operating alone or in conjunction with encoder 2514, includes in the response signal a superslot identifier that indicates the location of the superslot in the beaconslot where the base station received the access probe signal. . In some embodiments, an encoder module operating alone or in conjunction with encoder 2514 encodes sub-superslot timing correction information in a response signal, wherein the sub-superslot timing correction information is greater than the duration of the superslot. Indicates a small timing adjustment.

Access probe decoding and processing module 2548, operating alone or in conjunction with decoder 2512, may encode encoded information, eg, encoded superslot identifier, encoded information identifying a WT, access probe signal, or the like. To recover the encoded information, decode the received access probe signals.

In some embodiments, timing correction determination module 2550 is, for example, an integer multiple of the duration of the superslot from the difference between the decoded superslot identifier and the superslot index in the beaconslot of the superslot from which the access probe was received. Determine the main superslot timing offset correction. In some embodiments, timing correction determination module 2550 determines main superslot timing offset correction based on the beacon transmission reference point and the reference point of the received access probe signal. In some such embodiments, the access probe signal carries information indicating the index of the superslot in which the WT transmitted the access probe signal. In some such embodiments, the response signal carries access signal offset information not known to the BS but known to the WT and timing adjustment information combined by the WT. In some such embodiments, the sub-superslot timing correction is carried in the response signal via coded bits, while the main timing offset information is carried by the transmission time of the response signal.

The data / information 2522 may include a plurality of sets of information (user 1 / MN session A session B data / information 2554, user corresponding to the wireless terminal using the base station 2500 as a network connection point of the wireless terminals). N / MN session X data / information 2556). Such WT information may include, for example, data packets such as WT identifiers, routing information, assigned uplink single logical tones, downlink segment allocation information, user data / information such as voice information, text, video, music, etc. And a coded block of information. In addition, data / information 2522 includes downlink / uplink timing and frequency structure information 2576, beacon signal information 2558, received access probe signal information 2560, and response signal information 2562. System information 2574. The response signal information includes sub-superslot timing offset correction information 2252, and main superslot timing offset correction information 2564, superslot identifier information 2566, communication device identifier information 2568, and access probe identifier information. (2570).

In some embodiments, the main superslot timing offset correction is an integer multiple of the superslot time period. The superslot identifier may be used to indicate the location of the superslot in the beaconslot where the base station received the access probe signal to which the reception response corresponds. The communication device identifier may be used to identify the communication device from which the received response sent the corresponding access probe signal. The access probe identifier can be used to identify the access probe to which the response signal corresponds.

The downlink / uplink timing and frequency structure information 2576 is OFDM symbol transmission timing information, information corresponding to grouping of OFDM symbols, for example, slots, superslots, beacon slots, access intervals, information, beacons Timing and tone information, e.g., index information of superslots in a beacon slot, carrier frequency used for uplink and downlink, tone blocks used for uplink and downlink, uplink and downlink Tone hopping information, timing relationship and offset between the uplink and downlink timing structures at the base station, periodic intervals within the timing structures, and the like.

The techniques of the present invention may be implemented using software, hardware and / or a combination of software and hardware. The present invention relates to an apparatus, for example a mobile node such as a mobile terminal, a base station, and a communication system implementing the present invention. The invention also relates to methods, for example a method for controlling and / or operating a mobile node, a base station and / or a communication system, for example a host, in accordance with the invention. The invention also relates to a machine readable medium, eg, a ROM, a RAM, a CD, a hard disk, etc., comprising machine readable instructions for controlling a machine to implement one or more steps according to the invention.

In various embodiments, the nodes described herein are implemented using one or more modules to perform steps corresponding to one or more methods of the invention, eg, signal processing, message generation, and / or transmission steps. . Thus, in some embodiments various features of the invention are implemented using modules. Such modules may be implemented using software, hardware or a combination of software and hardware. Most of the methods or method steps described above may, for example, control a machine, eg, a general purpose computer with or without additional hardware, to implement all or some of the methods described above at one or more nodes. Can be implemented using machine executable instructions, such as software included in a memory device, eg, a machine readable medium, such as a RAM, a floppy disk, or the like. Thus, among others, the present invention relates to a machine-readable medium comprising machine executable instructions for causing a machine, eg, a processor and associated hardware, to perform one or more steps of the method (s) described above. .

The timing synchronization methods and apparatus of the present invention can be used by a wide variety of devices and systems. The method and apparatus of the present invention are well suited for use and are described in US Utility Patent Application No. 11 / 184,051, entitled “COMMUNICATIONS SYSTEM, METHODS AND APPARATUS”, filed on the same date as the present application and filed on the same date as the present application. It can be used in combination with the methods and apparatus. Such patent applications are expressly incorporated herein by reference and will be considered part of the specification of this patent application.

Although described in the context of an OFDM system, at least some of the methods and apparatus of the present invention are applicable to a wide range of communication systems, including many non-OFDM and / or non-cellular systems.

Many additional modifications to the method and apparatus of the present invention described above will be apparent to those skilled in the art in view of the above description of the present invention. Such changes will be considered within the scope of the present invention. In some embodiments, the base station functions as an access node to establish a communication link with a mobile node (WT) using OFDM signals. In various embodiments, the WT is implemented as a cell phone, a notebook computer, a personal digital assistant (PDA), or other portable device including receiver / transmitter circuitry and logic and / or routines for implementing the method of the present invention.

Claims (33)

Beacon time slots occur periodically, and a beacon signal is transmitted by the base station during each beacon time slot according to a periodic downlink timing structure, wherein the periodic downlink timing structure includes a plurality of beacon time slots in each beacon time slot. The superslots of the individual slots in the beacon time slot are identifiable through the use of a superslot index, each superslot comprising a plurality of symbol transmission time periods. As a method of operation, Receiving one or more beacon signals; Processing the received one or more beacon signals to determine a downlink timing reference point, wherein the superslots occur within a beacon time slot having a predetermined relationship to the determined downlink timing reference point. step; Coding the information in the first access probe signal identifying the first superslot index; Transmitting the first access probe signal identifying the first superslot index; Monitoring to determine whether a response to the first access probe signal has been received from the base station; And If it is determined that the response has been received, performing transmission timing adjustment as a function of information included in the response. The method of claim 1, And the first access probe signal is transmitted at a first timing offset relating to the start of a first superslot having the first superslot index. The method of claim 2, If it is determined that no response to the first access probe signal is received, Coding information in a second access probe signal identifying a second superslot index; And Transmitting the second access probe signal identifying the second superslot index at a second timing offset relative to the start of a second superslot having the second superslot index, as determined by the communication device. More steps, And the second timing offset is different than the first timing offset. The method of claim 3, wherein The first access probe signal and the second access probe signal are transmitted in different downlink beacon time slots, And the second superslot index is the same as or different from the first superslot index. The method of claim 4, wherein The first access probe signal and the second access probe signal are transmitted in different beacon time slots, And the second superslot index is different from the first superslot index. The method of claim 3, wherein The first access probe signal and the second access probe signal are transmitted in the same beacon time slot, And the second superslot index is different from the first superslot index. The method of claim 6, And the response comprises information identifying one of the probe signals being answered. The method of claim 3, wherein Coding information in a third access probe signal identifying a third superslot index; And Transmitting the third access probe signal at a third timing offset with respect to the start of a third superslot having the third superslot index, And the third timing offset is different from the first timing offset and the second timing offset. The method of claim 8, The second timing offset is different from the first timing offset by the sum of an initial timing offset value and a first integer multiple of the fixed step size timing offset, The third timing offset is different from the first timing offset by a sum of an initial timing offset value and a second integer multiple of the fixed step size timing offset, And a second integer multiple of said fixed step size timing offset is different from a first integer multiple of said fixed step size timing offset. The method of claim 9, The base station is a satellite base station, The round trip time between the satellite base station and the communication device for a signal traveling at the speed of light is greater than the duration of the superslot. The method of claim 10, And the round trip time is greater than 0.2 seconds. The method of claim 9, And the fixed step size timing offset is less than a duration of a base station access interval, which is a period of time during which the base station responds to the access probe signals. The method of claim 9, And wherein said fixed step size timing offset is greater than a duration of a symbol transmission period. The method of claim 9, And the first integer multiple and the second integer multiple are positive or negative. The method of claim 1, Determining a time to transmit the first access probe signal as a function of location information determined from a signal received from a terrestrial base station. The method of claim 15, Determining a time to transmit the first access probe signal is further performed as a function of known information indicative of the location of the terrestrial base station and the location of the satellite base station. The method of claim 1, And the first access probe signal is an OFDM signal. The method of claim 17, And the received one or more beacon signals are OFDM signals corresponding to a single OFDM tone. Beacon time slots occur periodically, and a beacon signal is transmitted by the base station during each beacon time slot according to a periodic downlink timing structure, the downlink timing structure comprising a plurality of superslots in each beacon time slot And wherein individual superslots in the beacon time slot are identifiable through the use of a superslot index, each superslot comprising a plurality of symbol transmission time periods, A receiver for receiving one or more beacon signals; A receive signal processing module for processing received signals, including received beacon signals, operative to determine a downlink timing reference point from the received one or more beacon signals, wherein the superslots are located at the determined downlink timing reference point. The received signal processing module occurring within a beacon time slot having a predetermined relationship to the received signal; A coding module for coding information in the first access probe signal identifying the first superslot index; A transmitter for transmitting the first access probe signal identifying the first superslot index; A monitoring module, used to determine whether a response to the first access probe signal has been received from the base station; And In response to the monitoring module, a timing correction module that performs transmission timing adjustment as a function of information included in the received access probe response. The method of claim 19, And the transmitter comprises means for transmitting the first access probe signal at a first timing offset relative to the start of a first superslot having the first superslot index. The method of claim 20, The coding module comprises means for coding information in a second access probe signal identifying a second superslot index if it is determined that a response to the first access probe signal has not been received; The transmitter comprises means for transmitting the second access probe signal identifying the second superslot index at a second timing offset with respect to the start of a second superslot having the second superslot index, And the second timing offset is different than the first timing offset. The method of claim 21, The transmitter transmits the first access probe signal and the second access probe signal transmitted in different beacon time slots, And the second superslot index is the same as or different from the first superslot index. The method of claim 22, The first access probe signal and the second access probe signal are transmitted in different beacon time slots, And the second superslot index is different than the first superslot index. The method of claim 21, The first access probe signal and the second access probe signal are transmitted in the same beacon time slot, And the second superslot index is different than the first superslot index. The method of claim 24, The response includes information identifying one of the probe signals being answered; The communication device further comprises a decoder module for decoding the information in the response identifying one of the probe signals. The method of claim 21, The coding module further comprises means for coding information in a third access probe signal identifying a third superslot index, The transmitter further comprises means for transmitting the third access probe signal at a third timing offset relative to the start of a third superslot having the third superslot index, And the third timing offset is different from the first timing offset and the second timing offset. The method of claim 26, Further comprising a storage device comprising stored fixed step size timing offset information, The second timing offset is different from the first timing offset by a first integer multiple of the stored fixed step size timing offset, The third timing offset is different from the first timing offset by a second integer multiple of the stored fixed step size timing offset, And said second integer multiple is different from said first integer multiple of said stored fixed step size timing offset. 28. The method of claim 27, The base station is a satellite base station, The round trip time between the satellite base station and the wireless terminal, for signals traveling at light speed, is greater than the duration of the superslot. 29. The method of claim 28, And the round trip time is greater than 0.2 seconds. 28. The method of claim 27, And said stored fixed step size timing offset is less than a duration of a base station access interval, which is a period of time said base station responds to said access probe signals. The method of claim 19, And the transmitter is an OFDM transmitter. The method of claim 19, Means for determining a time to transmit the first access probe signal as a function of location information determined from a signal received from a terrestrial base station. 33. The method of claim 32, And the communication device comprises stored information indicative of the position of the terrestrial base station and the position of the satellite base station.

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